San Francisco Building Inspection Commission Codes § 4.3 Risk-Targeted Maximum Considered Earthquake-Level Evaluation

Ground Motion: The ground motion representation for this evaluation shall be the Risk-Targeted Maximum Considered Earthquake (MCER) as defined in ASCE/SEI 7-16, Chapter 21.

A suite of not less than seven pairs of appropriate horizontal ground motion time series shall be used in the analyses. The selection and scaling of these ground motion time series shall comply with the requirements of ASCE/SEI 7-16, Chapter 16, with the following modifications:

a) The MCER response spectrum shall be the basis for ground motion time series scaling instead of the design

response spectrum.

• b) Either amplitude-scaling procedures or spectrum-matching procedures may be used.

c) Where applicable, an appropriate number of the ground motion time series shall include near fault and directivity effects such as velocity pulses producing relatively large spectral ordinates at relatively long periods.

Commentary: The procedures for selecting and scaling ground motion records, as presented here, represent the current state of practice. The procedures are written to retain some flexibility so that engineering judgment can be used to identify the best approach considering the unique characteristics of the site and the building.

Selection and scaling of earthquake ground motion records for design purposes is a subject of much current research. The Engineer of Record may wish to consider alternative approaches recently proposed; however, some of the proposed approaches have not been adequately tested on tall buildings so their adoption should only be considered with caution. Aspects of particular concern include the long vibration period of many tall buildings and the contributions of multiple vibration “modes” to key response quantities.

At near-fault sites, the average fault-normal response spectrum usually is larger than the average fault-parallel response spectrum due to the presence of a rupture directivity pulse in the fault-normal component of the ground motion. It is important to include in the suite of ground motions an appropriate number of motions that include nearfault and directivity effects so that design drift demands are appropriately determined, especially considering that Section 4.1 permits the design to be exempt from applying Equations 12.8-5 and 12.8-6 to drift calculations. If spectral matching is used, individual ground motion components should account for the distinction between faultnormal and fault-parallel hazard.

Mathematical Model: The three-dimensional mathematical analysis model of the structure shall conform to ASCE/SEI 7-16 Section 12.7.3.

The analyses shall consider the interaction of all structural and non-structural elements that materially affect the linear and nonlinear response of the structure to earthquake motions, including elements not designated as part of the lateralforce-resisting system in the code-level analysis (Section 4.1).

Commentary: This requires explicit modeling of those parts of the structural and non-structural systems that affect the dynamic response of the building. In addition, the effect of building response on all materially affected parts of the building must be evaluated.

The stiffness properties of reinforced concrete shall consider the effects of cracking and other phenomena on initial stiffness.

Commentary: In addition to cracking, effective stiffness can be affected by other phenomena. These include bond slip, yield penetration, tension-shift associated with shear cracking, panel zone deformations, and other effects.

The effective initial stiffness of steel elements embedded in concrete shall include the effect of the embedded zone. For steel moment frame systems, the contribution of panel zone (beam-column joint) deformations shall be included. The Engineer of Record shall identify any structural elements for which demands for any of the response-history runs are within a range for which significant strength degradation could occur, and shall demonstrate that these effects are appropriately considered in the dynamic analysis.

Commentary: For typical situations, element strength degradation of more than 20% of peak strength should be considered significant.

P-Δ effects that include all the building dead load shall be included explicitly in the nonlinear response history analyses.

Documentation submitted for Structural Design Reviewer review shall clearly identify which elements are modeled linearly and which elements are modeled nonlinearly. For elements that are modeled as nonlinear elements, submitted documentation shall include suitable laboratory test results or analyses that justify the hysteretic properties represented in the model.

The properties of elements in the analysis model shall be determined considering earthquake plus expected gravity loads. In the absence of alternative information, gravity load shall be based on the load combination 1.0 D + Lexp , where D is the service dead load and Lexp is the expected service live load.

Commentary: In typical cases it will be sufficient to take Lexp = 0.2 L , where L is the code-prescribed live load without live load reduction.

The foundation strength and stiffness contribution to the building seismic response shall be represented in the model. The foundation strength and stiffness characterization shall be consistent with the strength and stiffness properties of the soils at the site, considering both strain rate effects and soil deformation magnitude.

Analysis Procedure: Three-dimensional nonlinear response history (NLRH) analyses of the structure shall be performed. Inclusion of accidental torsion is not required. When the ground motion components represent site-specific fault-normal ground motions and fault-parallel ground motions, the components shall be applied to the threedimensional mathematical analysis model according to the orientation of the fault with respect to the building. When the ground motion components represent random orientations, the components shall be applied to the model at orientation angles that are selected randomly; individual ground motion pairs need not be applied in multiple orientations.

Commentary: Three-dimensional analyses are required to represent the inherent torsional response of the building to earthquake ground shaking. This is done by including in the NLRH model the actual locations and distribution of the building mass, stiffness, and strength. Accidental torsion is not required to be included in the NLRH analyses. (Accidental torsion is required for the code-level analysis of Section 4.1.)

The Engineer of Record shall report how damping effects are included in the NLRH analyses. The equivalent viscous damping level shall not exceed 5%, unless adequately substantiated by the Engineer of Record.

Commentary: The effects of damping in an analysis depend on the type of damping model implemented. Some models may overdamp higher modes or have other undesirable effects.

For each horizontal ground motion pair, the structure shall be evaluated for the following load combination: 1.0 D + Lexp + 1.0 E

Alternative load combinations, if used, shall be adequately substantiated by the Engineer of Record. Demands for ductile actions shall be taken not less than the mean value obtained from the NLRH. Demands for lowductility actions (e.g., axial and shear response of columns and shear response of walls) shall consider the dispersion of the values obtained from the NLRH.

Commentary: In typical cases the demand for low-ductility actions can be defined as the mean plus one standard deviation of the values obtained from the NLRH. Procedures for selecting and scaling ground motions, and for defining the demands for low-ductility actions, should be defined and agreed to early in the review process.

Acceptance Criteria: Calculated force and deformation demands on all elements required to resist lateral and gravity loads shall be checked to ensure they do not exceed element force and deformation capacities. This requirement applies to those elements designated as part of the lateral-force-resisting system in the code-level analysis (Section 4.1), as well as those elements not designated as part of the lateral-force-resisting system in the code-level analysis but deemed to be materially affected.

Commentary: Elements not designated as part of the lateral-force-resisting system in the code-level analysis (gravity systems) may be subjected to substantial deformations and forces, including axial forces accumulated over many stories, as they interact with the primary lateral-force-resisting system. Non-structural elements such as cladding are evaluated according to code requirements. This bulletin does not require checking non-structural elements at the MCER level.

The Engineer of Record shall identify the structural elements or actions that are designed for nonlinear seismic response. All other elements and actions shall be demonstrated by analysis to remain essentially elastic.

Commentary: Essentially elastic response may be assumed for elements when force demands are less than design strengths. Design strengths for non-ductile behaviors (e.g., shear and compression) of these essentially elastic elements are defined as nominal strengths, based on specified material properties, multiplied by strength reduction factors as prescribed in the SFBC. Design strengths for ductile behaviors of these essentially elastic elements are defined as nominal strengths, based on expected material properties, multiplied by ø =1.0. Alternative approaches to demonstrating essentially elastic response may be acceptable where appropriately substantiated by the Engineer of Record.

For structural elements or actions that are designed for nonlinear seismic response, the Engineer of Record shall evaluate the adequacy of individual elements and their connections to withstand the deformation demands. Force and deformation capacities shall be based on applicable documents or representative test results, or shall be substantiated by analyses using expected material properties.

The average result, over the NLRH analyses, of peak story drift ratio shall not exceed 0.03 for any story.

All procedures and values shall be included in the Seismic Design Criteria and are subject to review by the Structural Design Reviewer and approval by the Director.

Originally signed by: Isam Hasenin, P.E., C.B.O.,

Department of Building Inspection

Approved by the Building Inspection Commission on March 19, 2008

AB-084 Guidelines for the Structural Review of Continuous Tiedown Systems Used to Resist Overturning of Light-Framed Wood Shear Walls

NO. AB-084 : DATE : November 20, 2013 (Updated 01/01/2023 for code references) SUBJECT : Plan Check; Inspection

A “conventional” tiedown system typically utilizes cold-formed metal hardware bolted to the wood end posts of the shear wall and anchored to the foundation. Tensile overturning forces are carried by the wood end posts. A “continuous tiedown” system utilizes a continuous or coupled rod or cable assembly comprising bearing plates,

shrinkage compensating devices, and couplers, wherein tensile overturning forces are carried by the rod(s) or cable(s) not the wood end posts.

Continuous tiedown systems are not explicitly addressed by current prescriptive code requirements.

Plan check review and approval of continuous tiedown systems for any project shall be on a case-by-case basis in accordance with this Administrative Bulletin. The following requirements shall be the basis for plan check review and approval of continuous tiedown systems used within light-framed wood shear wall systems:

1. Shear walls shall be designed to comply with the drift requirements of ASCE 7-16 Section 12.8.6. Shear wall displacements shall be computed in accordance with CBC Section 2305.3. The component “da” of Equation 23-2 in

CBC Section 2305.3 shall include, but not be limited to, elongation of the rod or cable, and deformations and displacements of shrinkage compensating devices, coupling hardware and steel bearing plates.

2. In a multi-story shear wall installation, the continuous tiedown system shall be restrained by bearing plates at each story of the multi-story shear wall. Skipping of stories, where bearing plates are omitted at intermediate stories, resulting in multiple stories being tied together, is prohibited. Shrinkage compensating devices shall be provided at each story of the shear wall.

3. The computed rod or cable elongation or stretch, together with computed deformations of shrinkage compensating device in compliance with ICC AC-316, coupling hardware steel bearing plate and crushing of wood top plates, within any story under strength level (Load and Resistance Factor Design) short-term duration loading, such as wind or earthquake loads, shall not exceed 0.250 inch, and for working stress level (Allowable Stress Design) short-term loading, they shall not exceed 0.179 inch. Elongation or stretch shall be computed as the product PL/EAe, where P is the axial load (pounds), L is the initial rod or cable length at the story under consideration (inches), E is the

rod or cable modulus of elasticity (psi), and Ae is the effective tensile cross sectional area of the rod or cable (in² ).

4. Calculations demonstrating compliance with the foregoing shall be provided for plan check review.

5. Construction documents, signed and sealed by the engineer of record for the design of the building, shall specify the particular proprietary system or systems.

6. Any modification to the tiedown system proposed after a building permit has been approved shall require filing of a new permit application documenting the proposed modification. Plan check review of the proposed modification shall be in accordance with the requirements of this Administrative Bulletin.

7. Mixing of conventional and continuous tiedown systems within shear walls along a common line is prohibited.

8. In addition to other inspections required by SFBC 1705, special inspection of continuous tiedown systems shall be provided. In addition to structural observations required by SFBC 1704.6, the engineer of record for the design of the building shall provide structural observation of continuous tiedown installations, including shear wall boundary nailing, shear wall end post sizes, bearing plates, couplers, shrinkage compensating devices, and anchor bolts, to verify conformance of the installed tiedown system to the structural design intent. Originally Signed by:

Tom C. Hui, S.E., C.B.O., Director Department of Building Inspection

Approved by the Building Inspection Commission on May 18, 2011, revision approved 11/20/2013

San Francisco Environment Code Chapter 19 (Mandatory Recycling and Composting; Refuse Separation Ordinance); San Francisco Refuse Collection Space Design Guide; San Francisco Environment Code Section 902(b)(1).

DISCUSSION :

The City and County of San Francisco enforces state and local codes regarding Solid Waste Reuse and Recycling. These codes will help meet locally zero waste commitments of reducing total generation of solid waste in 2030 by at least 15% below 2015 levels, and reduction in solid waste disposal of at least 50% below 2015 levels. For the purpose of enforcement of these regulations in San Francisco, recycled materials are those which are diverted or recovered from the solid-waste stream. The word trash refers to materials that are non-recyclable and noncompostable.

This Administrative Bulletin details procedures for local enforcement of the requirements of state and local policies. These include the Model Ordinance adopted by the California Integrated Waste Management Board, Resolution 93-57 regarding Areas for Collecting and Loading Recyclable Materials in Development Projects. State law prohibited the issuance of permits for certain development projects after July 1, 2005 unless adequate space is provided for collection, storage, and conveyance of such materials. In addition, San Francisco Environment Code Chapter 19, Mandatory Recycling and Composting:

• Requires all persons in San Francisco to separate and deposit all recyclables, compostables or trash in appropriate containers designated for each type of refuse;

• Requires owners or managers of multifamily or commercial properties to provide adequate refuse collection service to tenants, employees, contractors, and customers of these properties; and

• Requires containers of appropriate number and size for the recyclable, compostable, and trash quantities reasonably anticipated to be generated at the location, with collection containers placed as close together as possible in order to provide all occupants with convenient access to containers designated for each type of refuse.

Well-designed refuse collection areas support successful participation in San Francisco’s mandatory recycling and composting programs that will apply when the building is completed.

Applicability

As detailed in the Model Ordinance and California Green Building Standards Code The following projects or portions of projects are required to provide adequate areas for collecting and loading recyclable materials, compostable organics, and trash:

• Newly constructed non-residential buildings (CalGreen 5.410.1);

• Newly constructed residential buildings with 5 or more dwelling units (CalGreen 4.410.2);

• Any new public facility where solid waste is collected and loaded, and any improvements for areas of a public facility used for collecting and loading solid waste;

• A new subdivision or tract of single-family detached homes if solid waste is collected and loaded in a location that services five or more living units;

• Any one of the above types of projects that is existing to which an addition is made that adds 30 percent or more to the existing floor area of the project;

• Any one of the above types of projects that is existing to which multiple additions are made over a one-year period that cumulatively add 30 percent or more to the existing floor area of the project;

• Any one of the above types of projects, occupied by multiple tenants, to which one or more tenant improvements are made under building permit over a one-year period by any one tenant that adds 30 percent or more to that tenant’s leased area, in which case that tenant’s leased area shall be provided with sufficient recycling areas;

In accordance with the City and County of San Francisco’s zero waste goal and targets and to facilitate compliance with mandatory recycling and composting requirements that will apply to the building when it is completed, the amount of space provided for the collection and storage of recyclable and compostable materials shall be sufficient to allow recovery of 100 percent of the facility’s recyclable and compostable materials and any remaining trash. Space shall be sufficient to accommodate containers consistent with both current methods and percentages of solid-waste storage and removal, and with projected needs when San Francisco’s zero waste goal is met.

All areas designated for the collection and loading of recyclable, compostable and trash materials shall be integrated into the design and, when appropriate, the structure of the project. Areas for recyclable and compostable materials shall be at least as convenient and usable as spaces provided for non-recyclable and non-compostable trash disposal, and shall be located in the same areas whenever possible. When separate locations must be provided due to space constraints, the locations for collection of recyclable and compostable materials shall be at least as convenient as trash disposal locations.

Each dwelling unit in a covered project shall include areas within the dwelling unit designed and designated for storage of recyclable, compostable and trash materials.

Any chute system for solid-waste disposal in a covered project must be designed for equal convenience to all users to separate the three refuse streams of trash, recycling and compostable materials.

Guidance in providing adequate areas for collecting and loading of recyclable, compostable and trash materials is available:

• The Department of the Environment (415-355-3700) has published the San Francisco Refuse Collection Space Design Guide and an Adequate Refuse Collection Space Calculator to estimate the floor area necessary to provide adequate space collecting and loading of recycling, composting, and trash service in San Francisco.. See https://sfenvironment.org/refusecalculator. For additional assistance:

• The City’s permitted refuse haulers will provide assistance in determining appropriate collection, storage and loading locations, dimensions and other requirements (for contact information please call the Department of the Environment at 415-355-3700);

• The California Integrated Waste Management Board, Planning and Assistance Division can provide a “Recycling Space Allocation Guide” and other assistance (916-322-4027). This publication is available at

https://www2.calrecycle.ca.gov/Publications/Details/832.

• US Green Building Council provides recycling area guidelines in various publications. Information is available on the USGBC website at www.usgbc.org/resources.

Submittals

For each covered project, the submittal documents accompanying the permit application shall provide sufficient detail to assure compliance with these requirements, including the following specific information:

1. Size and location of storage, collection and loading areas for all recyclable, compostable and trash materials, including space within individual dwelling units.

2. Type, size and number of collection containers for all recyclable, compostable and trash materials.

3. Type of proposed material handling equipment (e.g. compactors, balers, tippers, turntable systems, etc.)

4. Collection routes to conveniently access all recyclable, compostable and trash loading areas, including sufficient vertical and horizontal maneuvering clearances for collection vehicles.

5. Type and number of chutes proposed for recyclable, compostable and trash materials.

6. Signage for proposed collection, storage, and loading areas and containers.

7. Path-of-travel and other access for persons with disabilities to collection facilities, when required.

8. If not all in one location in the submittal documents, an index of locations in the submittal documents of the above required information.

Submittal documents will be reviewed by Department of Building Inspection staff, who may consult with staff of other agencies such as Department of the Environment.

When approved as part of a building permit, requirements for adequate areas for collecting and loading of recyclable, compostable and trash materials become part of the required building construction.

Maintenance of facilities

Maintenance of facilities designed for collection, storage and loading of recyclable, compostable and trash materials is required under San Francisco Existing Building Code 101.4.4.

Originally Signed by:

Isam Hasenin, P.E., C.B.O., Director

Department of Building Inspection

Approved by the Building Inspection Commission on March 19, 2008

Attachment A: Model Ordinance of the California Integrated Waste Management Board Relating to Areas for Collecting and Loading Recyclable Materials in Development Projects

requirements in effect at that time. Project sponsors should verify that they are meeting all applicable code requirements, which may modify the standards and procedures addressed in this Administrative Bulletin.

Green Building Requirements to be Applied

The San Francisco Green Building Code applies to all new construction in San Francisco, as well as most alterations and additions. To identify the green building requirements that apply to a project:

• Use Attachment A, Table 1 of this bulletin to find the overall green building standard [Leadership in Energy and Environmental Design (LEED), GreenPoint Rated, or ‘Locally Required Measures Only’] that applies, based on occupancy, project size, and whether the project is new construction or alteration. Attachment A, Table 1 also identifies the submittal required in order to confirm compliance with local requirements.

• Attachment B consists of four tables that summarize specific required measures:¹

• ° Table 1: Requirements for projects meeting a LEED standard

• ° Table 2: Requirements for projects meeting a GreenPoint Rated standard

• ° Table 3: Requirements for all non-residential projects that are not required to meet a LEED standard (includes certain new construction as well as certain additions and alterations)

• ° Table 4: Requirements for residential additions and alterations

For mixed occupancy buildings where local standards reference a green building rating system (Attachment A, Table 1), the project sponsor may apply a single green building rating system to the entire building. Each portion of the building must meet the Local Requirements applicable to that occupancy.

Applicability of Green Building Regulations Based on Date of Building Permit Application

Application of Green Building requirements is based on the date of submittal of a building permit application. The applicable date of the San Francisco Green Building Code 2022 is January 1, 2023. In the case of Site Permits, the effective date shall be the date that the Site Permit application (not an addendum) is filed with the Department of Building Inspection.

Table 1 summarizes the green building requirements that apply based on the date a complete application is submitted. Addenda to site permits and revisions to permit applications received before January 1, 2023 are required to meet the green building requirements that applied on the date a complete application for site permit was submitted. If a site permit addendum or revision changes the scope of the project such that current codes are generally applicable, then current green building requirements are also applicable.

For details, see the appropriate version of Administrative Bulletin 93: “Implementation of Green Building Regulations,” as summarized in the following table:

San Francisco Green Building Code (2016) January 1, 2017 through December January 2018 Revision 31, 2019 San Francisco Green Building Code (2013) January 1, 2014 through December January 1, 2014 31, 2016 San Francisco Building Code 13C (2010) July 18, 2012 through December 31, July 18, 2012 2013 San Francisco Building Code 13C (2010) January 1, 2011 through July 17, January 1, 2011 2012 San Francisco Building Code 13C (2007) November 3, 2008 through September 24, 2008 December 31, 2010

Applicability

Attachment A, Table 1 should be used to determine which green building requirements may apply to the project. Department of Building Inspection staff will screen all building permit applications to confirm which Green Building regulations apply, as summarized in Attachment A, Table 1. Every application for a Site Permit subject to these regulations must include a completed Green Building Site Permit Submittal (GS-1). Permit applications for new construction projects will not be accepted for processing without Green Building Site Permit Submittal GS-1, and permit applications for an addition or alteration will not be accepted without submittal GS-2, GS-3, GS-4, GS-5, or GS-6 as applicable.

At the time of the first architectural or superstructure addendum, whichever comes first, the submittal package for all applicable projects must include a checklist incorporated into the project plans indicating the required green building measures.² This checklist must reference, as appropriate, location of green building features in the submittal documents. The Green Building Submittal (GS-1, GS-2, GS-3, GS-4, GS-5, or GS-6) shall include this checklist, shall detail the green building requirements to be met, and shall indicate which addendum or other document will provide compliance details for each required performance measure or credit.

The Green Building Submittal may be reformatted as needed to conform to plan submittal size if all the required information is provided.

1. Registration and submittal for certification under LEED. For buildings that propose this option, the permit applicant must provide submittal documentation showing that the project will meet the appropriate LEED certification requirements. See the “Energy Compliance Guidelines for LEED projects” section below for details.

2. Registration and achievement of GreenPoint Rated status. For buildings that propose this option, the permit applicant must submit documentation showing that the project meets all requirements necessary to GreenPoint Rated certification.

3. Documentation of compliance with either LEED or GreenPoint Rated standards without registration and certification from those systems. The Green Building Compliance Professional of Record must provide submittal documentation showing that the project will meet the appropriate standards.

4. Registration and submittal for another rating system or documentation of equivalency as approved by the Director. For buildings that propose to meet such alternate standards, the Green Building Compliance Professional of Record must provide submittal documentation detailing compliance with the proposed standards.

5. Where neither LEED nor GreenPoint Rated is required, submit documentation of compliance with Locally Required Measures in effect at the time of permit submittal, as indicated.

Municipal projects³ of 10,000 square feet or larger are required to obtain LEED Gold certification by San Francisco Environment Code, Chapter 7. For such projects, only method 1) above may be used.

For methods 3), 4), and 5) above, the owner or owner’s agent must employ a Green Building Compliance Professional of Record who personally reviews and verifies compliance with San Francisco Green Building Code requirements, or who directly supervises persons providing on-site review or verification thereof.

For methods 3), 4), and 5) above, the qualifications for Green Building Compliance Professional of Record include a license or registration as an Architect or Engineer, and specialized understanding of Green Building standards and technologies:

• for LEED projects, such specialized understanding shall include LEED accreditation and successful completion of at least one LEED certified project.

• for GreenPoint Rated projects, such specialized understanding shall include the GreenPoint Rater designation, or the project team shall include a person who is a GreenPoint Rater.

• For projects solely required to meet Locally Required Measures, such specialized understanding, shall include either: International Code Council (ICC) Certified CalGreen Inspector certification, the GreenPoint Rater designation, LEED accreditation, or equivalent training and certification as approved by the Director.

For residential alteration and addition projects where the area of the project is less than 25,000 square feet and which increase total conditioned floor area of the building by no more than 1,000 square feet, a Green Building Compliance

Professional of Record is not required.⁴ In such cases, the applicant may complete the green building submittal. In all cases, applicable green building requirements apply to the entire project, and are not limited to the area of addition. The Department of Building Inspection may request verification of such training or experience and may make an administrative determination as to the qualification of a person to act as such a Green Building Compliance Professional of Record.

A Green Building Compliance Professional of Record is responsible for providing verification to the Department of Building Inspection that all Green Building design and construction requirements are met. Where a Green Building Compliance Professional of Record is responsible for verifying compliance with the requirements of the San Francisco Green Building Code, and no third party green building certification is to be achieved, project documents may be reviewed in detail in plan review and inspection, at standard hourly rates for staff time.

The 2022 San Francisco Green Building Code requires building permit submittals to show that they meet the compliance margin required by the applicable rating system or local code, and comply with the California Building Energy Efficiency Standards in effect at the time of permit submittal. In each case below, standard California Energy Standards documentation must be prepared using software approved by the California Energy Commission for demonstrating compliance with the applicable provisions and version of the California Energy Code. The following guidelines explain when additional calculations and documentation are required.

• Buildings meeting a LEED for Building Design and Construction (BD+C), or LEED Core and Shell standard for compliance with the San Francisco Green Building Code must prepare and submit all standard documentation required by the California Energy Commission to demonstrate compliance with the California Energy Standards (Title 24, Part

6. in effect on the date of permit application.⁶

• Where calculations based on Title 24 Part 6 California Energy Standards are used to document that ‘points’ are earned for energy efficient design and construction, the compliance margin cited in the applicable certificate of compliance (CF1R-PRF-01E for single family and NRCC-PRF-01 for commercial and multifamily) submitted for compliance may be utilized without modification. Residential all-electric buildings which demonstrate prescriptive

compliance and apply GreenPoint Rated J5.1 Option Two: All Electric Compliance may submit the applicable CF1R or NRCC report.

• Where the ASRHAE 90.1 option in LEED v4 (or subsequent) rules is used to document ‘points’ being voluntarily earned for energy-efficient design and construction, the supporting analysis must be submitted, and must include a detailed accounting of all on-site building energy use, including all: exterior and security lighting; elevators; process loads; and receptacle loads. Documentation to be retained in the records of the project must include all information required for LEED certification by the Green Building Certification Institute.

Buildings meeting a LEED for Homes or GreenPoint Rated standard must use California Energy Commissionapproved compliance software and submit documentation to demonstrate that the proposed building both:

• Complies with the California Energy Efficiency Standards in effect on the date of application for building permit, AND

• Meets the minimum energy performance requirements of the applicable green building rating system. Where California Energy Commission-approved compliance software is used to document the minimum energy efficiency requirements of the green building rating, all submittals related to compliance and the green rating system must be generated in a manner consistent with the guidance of the applicable green building rating system, and must faithfully represent the design as proposed. The most straightforward way to demonstrate compliance calculations are consistent with the calculations of the green building rating system is to use a single simulation run, so that the compliance run number is consistent throughout the compliance documentation.

San Francisco Building Code 106A.1.17.1 requires all-electric design and construction for all projects that submit an initial application for permit to construct new buildings on or after June 1, 2021. All space-conditioning, water heating, cooking, and clothes drying systems must be all-electric, and installation of infrastructure, piping systems, or piping for distribution of natural gas or propane to such uses indoors or outdoors is prohibited. The ordinance allows limited installation of gas piping systems for commercial food preparation, and if, after exhausting all options, allelectric construction is determined to be physically or technically infeasible. See Administrative Bulletin 112 for details.

Construction site runoff pollution prevention requirements depend upon project size, occupancy, and location in areas served by combined or separate sewer systems. Projects required to meet a LEED standard (see Attachment A, Table 1) must, at a minimum, prepare an erosion and sedimentation control plan per LEED Sustainable Sites prerequisite 1. However, more stringent local requirements may apply to any project, whether or not LEED is to be applied, such as a stormwater soil loss prevention plan or a Stormwater Pollution Prevention Plan (SWPPP). To confirm the construction site runoff pollution prevention requirements applicable to your project, please contact the SFPUC:

sfpuc.org/programs/pretreatment-program/construction-site-runoff.

Projects that disturb 5,000 square feet or more of ground surface in the separate and combined sewer areas, or that create or replace 2,500 square feet or more of impervious surface in separate sewer areas, must meet Stormwater Management Requirements as determined by the San Francisco Public Utilities Commission (SFPUC), and must submit a Stormwater Control Plan to the SFPUC for approval. The SFPUC has developed San Francisco Stormwater Management Requirements and Design Guidelines to aid project teams in meeting local requirements for stormwater controls, which are available online at: sfpuc.org/construction-contracts/design-guidelines-standards/water-efficientlandscape.

Projects that include at least 500 square feet of new or modified landscape are subject to the San Francisco Water Efficient Irrigation Ordinance.⁷ Details are available online at: sfpuc.org/smr.

New Large Commercial Interiors and Major Alterations to Existing Buildings

The application of San Francisco Green Building Code Sections 5.103.3 or 4.103.3 to Major Alterations to Existing Buildings is based on a determination as to whether a “significant upgrade” is proposed to both the structural system and to one or more of the mechanical, electrical and/or plumbing systems in an area of more than 25,000 gross square feet in a Group B, M or R occupancy. For the purpose of enforcement of the San Francisco Green Building Code, a significant structural upgrade shall be determined to take place when a structural alteration takes place in 30% or more of the area of proposed construction. Areas to be counted toward such a determination include areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered.

The application of Section 5.103.4 to New Large Commercial Interiors requires that the first time tenant improvement work in an area of at least 25,000 square feet must meet the green building standards detailed in the ordinance. This requirement applies regardless of the date of construction of the building, including the first time a space undergoes a tenant improvement after or concurrent with a major alteration as defined in San Francisco Green Building Code Section 202. Note that all first-time commercial tenant interior improvement work of less than 25,000 square feet must comply with all applicable CALGreen requirements; see Attachment B, Table 3 or Green Submittal Form GS-3 for details.

The construction of an accessory dwelling unit within an existing structure or attached to an existing structure is an alteration or addition. For the purpose of compliance with local amendments to California Green Building Standards, construction of a single freestanding dwelling unit accessory to an existing structure is considered an addition. See Green Submittal Form GS-5 for details.

Historic Building Requirements for “Historic Resources” Based on Planning Department Determination

For purposes of applying the specific provisions of the San Francisco Green Building Code related to historic buildings, the Planning Department shall determine whether a building is an historical resource. This Planning Department review applies a standard based on the California Environmental Quality Act (CEQA) as to whether a structure is or might be considered an “historic resource”. Based on such information, the Green Building Compliance Professional of Record shall confirm that submittal documents properly reflect the requirements of the Code. Projects which retain, rehabilitate or repair significant historical architectural features may receive credit toward Green Building requirements, per Attachment A, Table 3.

For buildings that are qualified to use the California Historical Building Code, project sponsors may apply the alternate provisions of that code. Buildings are determined to be qualified to use the California Historical Building Code upon specific request to the Department of Building Inspection. Buildings that qualify to use the California Historical Building Code include buildings that are on federal, state or local adopted lists or surveys, buildings that are determined by the City to be eligible for such a list or survey, or buildings that have otherwise been determined by the City to be potential historic resources. The applicant must confirm with the Department of Building Inspection whether code provisions for historic buildings will be applied to the entire building, specific items, or specific areas. Eligibility to use the California Historical Building Code is a separate process from the determination by the Planning Department that a building is an “historic resource,” but the Department of Building Inspection coordinates with the Planning Department on the review of requests for qualification to use the California Historical Building Code. Demolition

For a replacement building which is to be constructed on a site on which one or more buildings were demolished after the effective date of this ordinance, the Planning Department, during the course of permit review, shall confirm applicable Green Building requirements, as found in Attachment A, Table 2.

Project sponsors wishing to propose alternates or equivalencies for the specific requirements referenced in the San Francisco Green Building Code or its referenced standards may do so as described in Administrative Bulletin 5, “Procedures for Approval of Local Equivalencies.” Note that related state and local requirements continue to apply, including, but not limited to: California Green Building Standards Code (Title 24 Part 11); SFPUC Stormwater Management Ordinance; and SFPUC Water Efficient Irrigation Ordinance.

A proposal for an alternate or equivalent method of compliance may be submitted with initial permit application or at a later date. Proposals for alternate or equivalency to San Francisco Green Building Code must include:

1. Proposed approach. If more than one equivalency is proposed, each alternate must be presented separately.

2. Requests must be accompanied by a complete analysis of Green Building Code and other code-related issues, and must be recommended by and signed by the Green Building Compliance Professional of Record for the project. The analysis must include calculations or other documentation for each specific element, confirming that the proposal meets or exceeds the applicable requirements.

3. The Department of Building Inspection staff will review the proposal and may, at its discretion, request review by other City staff or other professionals expert in the subject matter under review. The project sponsor will be responsible for all additional costs incurred for such review, including review time by City staff, charged at the hourly rate as set forth in the San Francisco Building Code, or direct costs for other consultant review.

4. The Department of Building Inspection staff may request additional information as part of the review.

5. The Department of Building Inspection will issue a decision to approve, deny or require modifications to any submitted alternate or equivalency.

6. Project sponsors may appeal any decision to the Deputy Director, Director, and appeal bodies as detailed in the San Francisco Building Code.

Note that the 2022 San Francisco Green Building Code recognized GreenPoint Rated v.9 and all LEED v4 rating systems (see SFGBC 101.10), and allows the application of more recent versions of these rating systems. New residential projects of any size may therefore utilize LEED for Homes Midrise, LEED BD+C, or GreenPoint Rated without triggering the above process for confirming equivalency. Similarly, major alterations to residential buildings may use LEED for Building Design and Construction, GreenPoint Rated Multifamily New Home, or GreenPoint Rated Multifamily Existing Home to comply, provided applicable local requirements are met.

Alterations

Verification that green building requirements for new construction and major alterations have been met requires submittal of Attachment E, Green Building: Final Compliance Verification prior to final inspection. Attachment E may be completed using any of the following methods:

1. If the project has been submitted for certification under LEED, once certification is awarded the project sponsor shall provide documentation to the Department of Building Inspection that the Green Building Certification Institute has certified the project.

• 2. If the project has been submitted to be GreenPoint Rated, project shall provide to the Department of Building Inspection documentation that Build It Green has provided a GreenPoint Rated certificate to the project.
• 3. If the project is built to meet LEED or GreenPoint Rated standards but will not be certified, the Green Building Compliance Professional of Record must sign Attachment E.

4. If the Director has approved a proposal to modify local green building requirements on a case-by-case basis per Administrative Bulletin 005 ( Procedures for Approval of Local Equivalencies ), the Green Building Compliance Professional of Record must sign Attachment E and provide documentation the approved approach has been applied.

A Temporary Certificate of Occupancy may be issued pending final compliance certification. However, no final Certificate of Completion may be issued until Green Building Final Compliance Verification (Attachment E of this bulletin) has been received, reviewed, and accepted by the Department of Building Inspection.

Quality Assurance and Compliance Review

All projects are subject to comprehensive review by the Department of Building Inspection or its agents. Project sponsors must maintain comprehensive records to allow verification that all requirements have been met. Buildings that receive certification through LEED or GreenPoint Rated will generally be accepted as being fully compliant. The Department of Building Inspection may review any aspect of green building projects.

Failure to meet all required Green Building requirements will subject a project sponsor to all enforcement and abatement remedies detailed in the San Francisco Building Code.

Signed by:

Patrick O’Riordan, C.B.O. 4/16/2024

Director

Department of Building Inspection

Original version approved by the Building Inspection Commission on September 24, 2008, revision approved: 12/13/2023.

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1 Attachments are provided for reference only. For complete details on any specific requirement, refer to the San Francisco Green Building Code.

2 Such a checklist is required for each applicable project, including where Form 3 or Form 8 is used to apply for a permit.

3 Municipal projects, including leasehold improvements, are projects authorized by any department of the City and County of San Francisco. A municipal “leasehold” means a building or space where the City is a tenant.

4 Projects which are “major alterations” to residential occupancy (with project area of 25,000 square feet or greater; and significant structural upgrade; and significant mechanical, electrical, or plumbing) continue to require either registration and certification, or verification by a Green Building Compliance Professional of Record.

5 Procedures for verification of compliance for small residential alterations are subject to revision.

6 LEED BD&C (v4) and LEED CS (v4) minimum energy efficiency requirements are less strict than California 2013, 2016, 2019, and 2022 Title 24 Part 6 Energy Standards.

7 The San Francisco Water Efficient Irrigation Ordinance is stricter than both the landscape irrigation efficiency measures in California’s Green Building Standards (Title 24 Part 11) as well as California’s Model Water Efficient Landscape requirements (AB 1881.)

Attachment A, Table 1: Summary of Requirements

Attachment A, Table 2: Additional Requirements in Case of Demolition

Attachment A, Table 3: Reduced Requirements for Retention of Significant Historical Architectural Features Attachment B, Table 1: Requirements for Projects Meeting a LEED Standard

Attachment B, Table 2: Requirements for Projects Meeting the GreenPoint Rated Standard

• Attachment B, Table 3: Requirements for All Non-residential Projects Not Required to Meet a LEED Standard Attachment B, Table 4: Requirements for Residential Additions and Alterations

• Attachment C: Instructions for Green Building Submittals

• Forms for Submittal:

• GS-1: Green Building Site Permit Submittal Form

• GS-2: Green Building Submittal Form for LEED or GreenPoint Rated Projects

• GS-3: Green Building Submittal Form for Other Non-Residential Alterations, Additions & New Construction

• GS-4: Green Building Submittal Form for Non-residential Interior-only Alteration Projects

• GS-5: Green Building Submittal Form for Residential Alteration + Addition Projects

• GS-6: Green Building Submittal Form for Municipal Projects

• Attachment D: Supplementary Energy Compliance Documentation

• Attachment E: Final Compliance Verification

• Attachment F: Recommended Project Implementation Procedures

• Attachment G: Selected Green Building Resources Attachment H: Review of Energy Performance Requirements

AB-094 Definition and Design Criteria for Voluntary Seismic Upgrade of Soft- Story, Type V (Wood-Frame) Buildings

Permits for voluntary structural work that do not reference meeting a specific code standard or that do not qualify for incentives for voluntary seismic upgrade work permit processing may meet any level of upgrade if such work does not increase the hazard of the building.

Chapter 5E of the San Francisco Existing Building Code requires the mandatory retrofit of Soft Story Type V (woodframe) buildings, built prior to 1978 with 2 or more stories over a weak story and having 5 or more residential units. Buildings falling within the scope of SFEBC Chapter 5E are not eligible for the incentives offered in this bulletin. The application and incentives of AB-094 apply to buildings with 4 or fewer residential units or other occupancy classifications.

Building owners who wish to take advantage of voluntary seismic upgrade incentives must meet the definition of a soft-story Type V (wood-frame) building and must comply with the retrofit standards as detailed below.

DEFINITIONS

For the purpose of this Administrative Bulletin the following definitions shall apply:

Soft-story Type V (wood-frame) building means a building that meets the following criteria:

• A. a Type V (wood-frame) building as defined in the San Francisco Building Code, and

• B. was constructed prior to May 21, 1973, and

• C. has a ground floor (1st story) level in which

• a. at least 50% of the floor area of the ground floor is used for Occupancy Classifications A (assembly), B

• (business), M (mercantile), S (storage, open or enclosed parking garages), or U (private garages), or

b. the building has been determined to have either a Weak Story or Soft Story deficiency when evaluated using the ASCE 31 Tier 2 procedure, or

• c. the building has been determined to have a soft-story deficiency based on engineering analysis acceptable to the Building Official.

The standards to be applied to the seismic upgrade of soft-story wood-framed buildings in order to qualify for voluntary upgrade incentives shall be one of the following:

• A. Meets the requirements of Appendix A - Chapter A4 of the California Existing Building Code, CEBC, or

• B. Meets the requirements of ASCE 41 for the Partial Rehabilitation Objective (Section 1.4.3) (Life Safety Performance Level: S-3) in the BSE-1 earthquake hazard level, or

C. Meets any other alternate rational design and/or construction methodology that demonstrates compliance with the intent of San Francisco Existing Building Code Section 304.4. For qualified historic buildings, seismic upgrade designs may use the provisions and analysis techniques referenced in the California Historical Building Code, Chapter 8-7, Structural Regulations, and Chapter 8-8, Archaic Materials and Methods of Construction to assist in meeting the retrofit standards.

For the purposes of this bulletin, mitigation of the soft-story conditions at the ground floor (1st story) shall be considered the part of the voluntary soft-story wood-frame upgrade work eligible for incentives. Additional seismic upgrade work may be undertaken on the floors above the ground floor; however such additional seismic retrofit work is not considered part of the voluntary soft-story upgrade work and will be subject to standard permitting requirements.

Submittal Documents and Building Permit Application

Building permit applications for voluntary, soft-story Type V (wood-frame) building upgrade work must clearly state the intention to qualify for voluntary incentives in the Project Description portion of the building permit application form. Submittal documents should include the following:

A. Dimensioned plans showing all exterior walls, interior partitions and any lateral load-resisting, or plans showing Occupancy Classifications and uses of the ground floor if that is the method of qualifying as a soft-story building under this Administrative Bulletin, and

• B. A photograph of the building exterior, and

C. Structural upgrade plans and necessary supporting calculations and documents prepared by a licensed design professional showing how seismic upgrade will meet the standards adopted in this Administrative Bulletin. Included in these submittal documents should be a listing of archaic materials and values for those materials, if these are to be used as part of the lateral force resisting system.

Building permit applications for voluntary soft-story wood-frame seismic retrofit will be expedited as authorized under AB-004 and will be tracked by the Department of Building Inspection for reporting purposes. Originally signed by:

Vivian L. Day, C.B.O. April 21, 2010

Director

Department of Building Inspection

Approved by the Building Inspection Commission on April 21, 2010

Attachment: Excerpts from Ordinance 54-10, Seismic Strengthening of Soft-Story, Wood-Frame Buildings

202 as, in essence, a loss of lateral capacity of 20 percent or more in any horizontal direction. The code does not give specific rules for identifying a 20-percent capacity loss nor guidance as to how to calculate capacity loss, so implementation of these code provisions relies on interpretation by the Department of Building Inspection. This Bulletin presents the Department’s interpretation of 20-percent lateral capacity loss in terms based on visual indicators of such damage, and details the scope of required retrofit for buildings that exhibit earthquake-induced substantial structural damage.

In addition to substantial structural damage, San Francisco Existing Building Code Section 405.2 triggers structural evaluation and possibly retrofit when earthquake-related damage reaches the level of disproportionate damage, which is defined in Section 202 as, in essence, a lateral capacity loss of 10 percent or more in an earthquake of limited intensity. This Bulletin presents the Department’s interpretation of a 10-percent capacity loss based on visual indicators of such damage and provides evaluation and retrofit scope for buildings with such earthquake induced disproportionate damage.

Residential buildings that incur substantial structural damage or disproportionate damage as detailed in this Bulletin are considered to be “substandard” per California Health and Safety Code Section 17920.3 (b) Structural hazards and (o) Inadequate structural resistance to horizontal forces.

APPLICABILITY

A building is eligible to apply the interpretations and provisions of this Bulletin if all of the following criteria are met: A. The building has at least one story in which the seismic force-resisting system is a wood light-frame system in at least one direction, and

• B. The building has only wood floor and wood roof diaphragms, and

• C. The building has a continuous foundation, and

• D. The building contains a residential occupancy group R-1, R-2, R-3.1, or R-4 as defined in San Francisco

Building Code Section 310. At the discretion of the Department of Inspection, a building in occupancy group R-3 with one or two residential units may be deemed eligible if it is structurally and architecturally similar to the typical residential buildings with three or more units addressed in this Bulletin.

Buildings of other construction types and occupancies may also apply the provisions of this Bulletin on a case-by-case basis when approved by the Department of Building Inspection. Other methods of determining capacity loss based on analysis, testing, or other objective data may be allowed at the discretion of the Department.

Qualified historic buildings are permitted to be evaluated or retrofitted using the provisions in the California Historical Building Code, provided that such standards do not result in seismic performance less than the evaluation and retrofit engineering criteria detailed in this Bulletin.

For the purpose of determining if a building has incurred substantial structural or disproportionate damage, visual observation and classification of damage patterns may be used in lieu of a calculation of percentage loss of capacity. All determinations of substantial structural or disproportionate damage, including visual observation and classification of damage, shall be made by a licensed design professional and shall be submitted in accordance with San Francisco Existing Building Code Section 405.2.3.1. For damage not deemed to be either substantial structural damage or disproportionate damage, repairs shall restore the building to its permitted pre-earthquake condition by methods acceptable to the Department.

Substantial structural damage to vertical elements of the lateral force-resisting system shall be deemed to exist when a “triggering damage pattern” is observed in any system or components listed in Table 1. Table 1 also includes earthquake-induced substantial structural damage indicators for gravity load-carrying components. These are defined in San Francisco Existing Building Code, Section 202 as “any component, or any group of such components, that

supports more than 30 percent of the total area of the structure’s floor(s) and roof(s),” and the remaining capacity of any damaged components, “with respect to all dead and live loads, is less than 75 percent of that required by this code for new buildings of similar structure, purpose and location.” Per San Francisco Existing Building Code, Section 502.2, the provisions of this Bulletin apply to substantial structural damage to gravity load-carrying components only when that damage has been caused by earthquake.

Disproportionate damage to vertical elements of the lateral force-resisting system shall be deemed to exist when any of the earthquake “triggering damage patterns” is observed in any system or component listed in Table 1. Table 1 also includes disproportionate damage indicators for gravity load-carrying systems, which include any component, or any group of components, that supports more than 10 percent of the total area of a structure’s floor(s) and roof(s), and in which the remaining capacity of any damaged components, with respect to all dead and live loads, is less than 75 percent of that required by this code for new buildings of similar structure, purpose and location. The provisions of this Bulletin apply to disproportionate damage to gravity load-carrying components only when such damage has been caused by earthquake, as SFEBC Section 405.2.2 notes that a building with disproportionate damage is subject to the provisions and requirements for substantial structural damage.

Table 1: Substantial Structural Damage and Disproportionate Damage Patterns for Wood Frame Residential Buildings with Three or More Dwelling Units

When any of the following damage patterns is along a wall line. observed:

• Failure of diaphragm-to-wall connections at rim joist or blocking, or

• Collector or chord failure.

For buildings with substantial structural damage, further evaluation and retrofit shall proceed in accordance with San Francisco Existing Building Code Section 405.2.3.1 subject to the following guidelines:

A. Evaluation and retrofit shall consider the entire structure, including all stories and all directions, regardless of where in the structure the triggering damage occurred, except that for certain building types and damage patterns, partial retrofit may be permitted under one of the alternative criteria documents given in the “Evaluation and Retrofit Engineering Criteria” section of this Bulletin.

B. Gravity load-carrying components need not be considered for evaluation and retrofit except when they are also part of the building’s seismic force-resisting system or are subject to San Francisco Existing Building Code Section 502.2.

C. Nonstructural components need not be considered for evaluation or retrofit unless subject to separate building code requirements, ordinances, or regulations.

D. Load combinations that include wind or earthquake effects shall be considered.

For buildings with disproportionate damage, further evaluation and retrofit shall proceed in accordance with San Francisco Existing Building Code Section 405.2.2 subject to the following guidelines:

A. Evaluation and retrofit shall consider the entire structure, including all stories and all directions, regardless of where in the structure the triggering damage occurred, except that for certain building types and damage patterns, partial retrofit may be permitted under one of the alternative criteria documents given in the “Evaluation and Retrofit Engineering Criteria” section of this Bulletin.

Exception: When the disproportionate damage is limited to connections or load path elements and does not affect wood-frame wall segments, piers, or other vertical elements of the lateral force-resisting system, the evaluation and retrofit scope may be limited to components throughout the building in directions similar to or performing the same function as the components with damage.

B. Gravity load-carrying components need not be considered for evaluation and retrofit except when they are also part of the building’s seismic force-resisting system or are subjected to San Francisco Existing Building Code Section 502.2.

C. Nonstructural components need not be considered for evaluation and retrofit unless subject to separate building code requirements, ordinances, or regulations.

D. Load combinations that include earthquake effects shall be considered. Load combinations that include wind effects may be ignored.

If, after evaluation, the pre-earthquake building is determined to satisfy the criteria of San Francisco Existing Building Code, Section 405.2.3, then the building need not be retrofitted, but shall be restored to its pre-earthquake capacity. When retrofit is triggered by earthquake damage at any level, the engineering criteria for retrofit shall be permitted to use earthquake loads that are 75 percent of those prescribed by the San Francisco Building Code for new construction, in accordance with SFEBC Section 405.2.3.

Alternatively, any of the following codes, standards, or guidelines may be used as alternative evaluation or retrofit criteria for qualifying buildings:

• A. Meets ASCE 31-03 for the Life Safety Performance Level, or

B. Meets ASCE 41-06 for the Life Safety Performance Level (S-3) in a BSE-1 earthquake hazard level, or

C. If the triggering damage involves only a soft, weak, or open front first story, meets CEBC Appendix A - Chapter A4 or IEBC Appendix A - Chapter A4 with NCSEA/SEAOC amendments, or

D. Meets San Francisco Existing Building Code Section 304.4.

Originally Signed by:

Tom C. Hui, S.E. July 2, 2012

Acting Director

Department of Building Inspection

Approved by the Building Inspection Commission on June 20, 2012.

AB-099 Post-Earthquake Repair and Retrofit Requirements for Concrete Buildings

NO. AB-099 : DATE : July 2, 2012 (Updated 01/01/2023 for code references) SUBJECT : Permit Review and Operations TITLE : Post-Earthquake Repair and Retrofit Requirements for Concrete Buildings PURPOSE : The purpose of this Bulletin is to establish policy for interpreting the San Francisco Building Code regarding post-earthquake damage retrofit triggers for concrete buildings constructed before May 21, 1973 and to detail the scope and criteria for such triggered retrofits and other repairs. REFERENCES : Current edition of the San Francisco Existing Building Code - Section 202, Definition of Disproportionate Earthquake Damage - Section 202, Definition of Substantial Structural Damage - Section 304.4, Minimum Lateral Force for Existing Buildings - Chapter 4, Repairs Current edition of the California Historical Building Code, CCR Title Part 8 ASCE/SEI Standard 31, Seismic Evaluation of Existing Buildings ASCE/SEI Standard 41, Seismic Rehabilitation of Existing Buildings, with Supplement 1 California Health and Safety Code, Section 17920.3 CAPSS Report, Here Today – Here Tomorrow: The Road to Earthquake Resilience in San Francisco , PostEarthquake Repair and Retrofit Requirements (ATC-52-4 Report), https://sfgov.org/sfc/sites/default/files/ESIP/FileCenter/Documents/9761- atc524_compressed.pdf FEMA 273: NHERP Guidelines for the Seismic Rehabilitation of Buildings FEMA 306: Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings: Basic Procedures Manual FEMA 308: The Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 356: Prestandard and Commentary for the Seismic Rehabilitation of Buildings (FEMA, 2000) DISCUSSION : San Francisco Existing Building Code, Section 405.2.3 triggers seismic evaluation, and possibly retrofit, of buildings when earthquake-related damage reaches the level of “substantial structural damage to vertical elements of the lateral-force-resisting system.” Substantial structural damage is defined in Section 202 as, in essence, a loss of lateral capacity of 20 percent or more in any horizontal direction. The code gives no specific rules for identifying a 20-percent loss or guidance as to how to calculate capacity loss, so implementation of these code provisions relies on interpretation by the Department of Building Inspection. This Bulletin presents the Department’s interpretation of a 20-percent lateral capacity loss for concrete buildings constructed before May 21, 1973.

In addition to substantial structural damage, San Francisco Existing Building Code, Section 405.2 triggers seismic evaluation, and possibly retrofit, when earthquake-related damage reaches the level of disproportionate damage, defined in Section 202 as, in essence, a lateral capacity loss of 10 percent or more in an earthquake of limited intensity. This Bulletin presents the Department’s interpretation of a 10-percent capacity loss for concrete buildings constructed before May 21, 1973.

For concrete shear wall and infill buildings, the evaluation procedures developed in FEMA 306 and the simplified version of the methodology in FEMA 308 are used determine whether a building with substantial structural damage or disproportionate damage needs to be restored to its pre-earthquake capacity or retrofitted. Substantial structural damage or disproportionate damage may also be deemed to exist when damage to specific building components or conditions reaches the severity of “earthquake triggering damage” based on visual observation and classification. For concrete moment-frame buildings, repair and retrofit requirements are based only on visual observation and classification of specific components damage.

Residential buildings that incur substantial structural damage or disproportionate damage as detailed in this Bulletin are considered to be “substandard” per California Health and Safety Code Section 17920.3(b) Structural

APPLICABILITY:

A building is eligible to apply the interpretations and provisions of this Bulletin if all of the following criteria are met:

• A. The building has cast-in-place concrete bearing walls or cast-in-place concrete frames, and

• B. The building has at least one floor diaphragm constructed with cast-in-place concrete.

Buildings of other construction types may also apply the provisions of this Bulletin on a case-by-case basis when approved by the Department of Building Inspection. Other methods of determining capacity loss based on analysis, testing, or other objective data may also be allowed at the discretion of the Department.

Qualified buildings may be permitted to be evaluated or retrofitted using the provisions in the California Historical

Building Code, provided that such standards do not result in seismic performance less than the evaluation and retrofit engineering criteria detailed in this Bulletin.

For the purpose of this bulletin, the following definitions shall apply:

• CONCRETE SHEAR WALL: A concrete wall which resists lateral forces applied parallel to the plane of the wall.

• CONCRETE MOMENT FRAME: A building frame system in which seismic shear forces are resisted by shear

• and flexure in members and joints of the frame, including slab-column moment frames.

• CONCRETE INFILL FRAME: A concrete moment frame having panel(s) of masonry that participate in

• resisting lateral forces that are placed within the frame members.

• NONSTRUCTURAL REPAIR: Repairs that improve the visual appearance of damage to a component. These repairs may also restore the nonstructural properties of a component, such as weather protection. Any structural benefit is negligible. This is defined as “Cosmetic Repair” in FEMA 308.

Concrete Shear Wall and Infill Frame Buildings

General

Substantial structural damage to elements of the lateral force-resisting system shall be deemed to exist when the results of a FEMA 306 evaluation shows that capacity loss exceeds 20% for a concrete shear wall or infill frame building, or when any of the “triggering damage” criteria for substantial structural damage described in Table 1 is observed in an eligible building.

Additionally, disproportionate damage shall be deemed to exist when a FEMA 306 evaluation shows a capacity loss exceeding 10%, or when any of the “triggering damage” for disproportionate damage described in Table 1 is observed in an eligible building.

The flowchart in Figure 1 shall be followed to determine the post-earthquake damage repair or retrofit requirements related to substantial structural damage to concrete shear wall and infill frame buildings.

The process begins with a determination of whether the damaged building has sufficient pre-earthquake capacity to satisfy San Francisco Existing Building Code, Section 304.4, which references the May 21, 1973 milestone requirements of San Francisco Existing Building Code, Section 304.4. If the building in its pre-damaged state satisfies this code provision, then the building need not be retrofitted regardless of the level of damage, and restoration to preearthquake capacity is sufficient. Alternatively, if a full FEMA 306 evaluation (labeled as “Optional FEMA 306 Evaluation” in Figure 1) shows a capacity loss of less than 5 percent, nonstructural repair to the building instead of restoration to pre-earthquake capacity shall be permitted, except that individual component damage or condition repair per Table 1 is also required.

If the building does not meet the San Francisco Existing Building Code, Section 304.4 requirements per San Francisco Existing Building Code Section 304.4, then a full FEMA 306 evaluation (labeled as “Mandatory FEMA 306 Evaluation” in Figure 1) is required, and nonstructural repair, restoration to pre-earthquake capacity, or retrofit requirements may be triggered as shown in Figure 1. In addition, individual component damage or condition repair per Table 1 is required.

FEMA 306 Evaluation Process

A FEMA 306 evaluation process for the pre-event structure and the damaged structure shall be performed using the guidelines below:

1. The evaluation shall use the nonlinear static procedures defined in FEMA 306 to determine the capacity for preevent and damaged conditions. FEMA 306 was developed at the time FEMA 273 was also in development, prior to the publication of FEMA 356. Since then, additional research and development effort was incorporated into FEMA 356 and later into ASCE 41. Therefore, the comparable, more current equations in ASCE 41 shall be used in performing a FEMA 306 evaluation rather than the FEMA 273 equivalents.

2. The global displacement demand shall be determined in accordance with ASCE 41.

3. The performance objective shall meet the requirements of ASCE 41 for Life Safety Structural Performance Level (S-3) at 75% of the spectral demand associated with the current code value at the building site.

The following simplified version of the FEMA 308 approach, based on loss in performance, L, may be used for the purpose of determining threshold triggers for restoration to pre-earthquake capacity and retrofit. The process is similar to that outlined in Figure 1. The FEMA 308 parameters shall be determined using the guidelines as follows. For further definition of the FEMA 308 parameters needed for the evaluation.

1. To use this method, first determine the following performance capacity and loss indices:

P = dc / dd ,

where dc is the global displacement capacity for the selected performance objective and dd is the maximum global

displacement demand for the selected ground motion. This performance index is calculated using component properties for the pre-event conditions in accordance with the methodology outlined in FEMA 306.

• Damaged Performance Index:

P’ = d’c / d’d ,

where the prime symbol (’) denotes that the global displacement capacity and demand, d’c and d’d , respectively, are determined for the components in their damaged state using FEMA 306.

• Loss :

where L is the performance loss of a building due to earthquake damage, and is given by the ratio of the damaged performance index, P’ , to the undamaged performance index, P , for a specific performance objective. L ranges between 0 and 1.

3. To determine whether earthquake damage is acceptable and neither restoration to pre-earthquake capacity nor retrofit is triggered, the performance loss, L , is compared against the FEMA 308 Table 3-1 threshold parameters defined below:

• Lr(min) : The Loss threshold below which neither restoration to pre-earthquake capacity nor retrofit is triggered,

• shall be defined as follows:

• Lr(min) = 0.05 for earthquake event with Sa0.3 ≤ 0.4g

• Lr(min) = 0.05 for earthquake event with Sa0.3 > 0.4g

• Lr(max) : The Loss threshold above which either restoration to pre-earthquake capacity or retrofit is triggered. For

• this simplified procedure, Lr(max) may be taken to be the same as Lr(min) since Lr does not vary: Lr(max) = 0.05 for earthquake event with Sa0.3 ≤ 0.4g

• Lr(max) = 0.05 for earthquake event with Sa0.3 > 0.4g

Alternatively, the Damaged Performance Index, P’ may be used to determine whether earthquake damage is acceptable and neither restoration to pre-earthquake capacity nor retrofit is triggered by comparing P’ against the FEMA 308 Table 3-1 limit parameters defined below:

• P’min : The Damage Performance Index limit below which restoration to pre-earthquake capacity or retrofit is

• triggered, is not used since Lr does not vary for the simplified method.

• P’max : The Damage Performance Index limit above which neither restoration to pre-earthquake capacity nor

• retrofit is triggered regardless of the value of Loss, L , shall be defined as 1.0.

4. If a building is required to be restored to its pre-earthquake capacity or retrofitted per step 2, the Performance Loss, L , is compared against the FEMA 308 Table 3-2 threshold parameters defined below to determine if retrofit is triggered:

• Lu(min) : The Loss threshold below which earthquake damage does not trigger retrofit but requires restoration to

• pre-earthquake capacity, shall be defined as below:

• Lu(min) = 0.10 for earthquake event with Sa0.3 ≤ 0.4g

Lu(min) = 0.20 for earthquake event with Sa0.3 > 0.4g

• Lu(max) : The Loss threshold above which earthquake damage triggers retrofit, shall be taken to be the same as

• Lu(min) since Lu does not vary for the simplified method:

• Lu(max) = 0.10 for earthquake with Sa0.3 ≤ 0.4g

Lu(max) = 0.20 for earthquake with Sa0.3 > 0.4g

Alternatively, the Undamaged Performance Index, P may be used to determine whether restoration to pre-earthquake capacity or retrofit is triggered by comparing P against the FEMA 308 Table 3-2 limit parameters defined below:

• Pmin : The Pre-event Performance Index limit below which existing earthquake damage triggers retrofit, is not used

• since Lu does not vary for the purpose of the simplified method.

• Pmax : The Pre-event Performance Index limit above which existing earthquake damage does not trigger retrofit and

• restoration to pre-earthquake capacity is sufficient regardless of the value of Loss, L , shall be taken as 1.0.

In addition to the retrofit triggers per the FEMA 306 and 308 methodologies described above, damage to any of the specific components or other conditions noted in Table 1 below shall trigger retrofit shown in the “Action Required” column of the table if damage is observed to reach the severity of “triggering damage.” The conditions noted in Table

1 are primarily related to gravity-load-carrying component damage, load path failures, or significant damage in individual components. For damage less than the “triggering damage,” repairs shall be made to return the building to original strength or condition by methods acceptable to the Department of Building Inspection.

Table 1: Triggers for Specific Components or Conditions in Concrete Buildings

The process for determining whether repair or retrofit is triggered for a concrete moment-frame building begins with a determination of whether the damaged building has adequate pre-earthquake capacity to comply with San Francisco Existing Building Code, Section 304.4. If this is satisfied, then the building need not be retrofitted regardless of the level of damage, and restoration of the building to its pre-earthquake capacity shall be undertaken. Unlike concrete shear-wall and infill buildings, nonstructural repairs shall not be permitted even if a full FEMA 306 evaluation has determined that the capacity loss is below 5 percent. For non-complying buildings, if any of the component damage or conditions given in Table 1 is present, the building shall be retrofitted as required by Table 1.

For concrete frame buildings with any interacting walls, in addition to the Table 1 checks, the evaluation procedure and retrofit scope given above for concrete shear wall and infill frame buildings shall be applied. When a FEMA 306 analysis is used to determine loss of capacity outlined in this bulletin for concrete shear wall and infill frame

buildings, the moment-frame capacity may not be included in development of the force-displacement pushover curve.

When retrofit is triggered by earthquake damage at any level, the engineering criteria for retrofit shall be permitted to use earthquake loads that are 75 percent of those prescribed by the San Francisco Building Code for new construction, in accordance with SFEBC Section 405.2.3.

In addition, any of the following alternative codes, standards, or guidelines may be used as alternative evaluation or retrofit criteria for qualifying buildings:

• A. Meets the requirements of ASCE 31-03 for the Life Safety Performance Level, or

• B. Meets the requirements of ASCE 41-06 for the Life Safety Performance Level (S-3) in the BSE-1 earthquake hazard level, or

• C. Meets the requirements of San Francisco Existing Building Code 304.4.

Originally Signed: Tom C. Hui, S.E. July 2, 2012 Acting Director Department of Building Inspection Approved by the Building Inspection Commission on 6/20/2012

NO. AB-100 : DATE : July 12, 2012 (Updated 01/01/2023 for code references) SUBJECT : Permit Review and Operation TITLE : Post-Earthquake Repair and Retrofit Requirements for One- and Two-Family Units PURPOSE : The purpose of this Bulletin is to establish policy for interpreting the San Francisco Building Code regarding post-earthquake damage retrofit triggers for one- and two-family dwellings of wood-frame construction and to detail the scope and criteria for such triggered retrofits. The Bulletin also provides guidance on the scope of required building repair if retrofits are not triggered. REFERENCES : Current edition of the San Francisco Existing Building Code - Section 304.4, Minimum Lateral force for existing buildings - Section 202, Definition of Disproportionate Earthquake Damage - Section 202, Definition of Substantial Structural Damage - Chapter 4, Repairs Current edition of the California Historical Building Code, C.C.R. Title Part 8 Current edition of the California Existing Building Code, Appendix A - Chapter A4, or the current edition of the International Existing Building Code, Appendix A - Chapter A4 with NCSEA/SEAOC amendments ASCE/SEI Standard 31, Seismic Evaluation of Existing Buildings ASCE/SEI Standard 41, Seismic Rehabilitation of Existing Buildings, with Supplement 1 California Health and Safety Code, Section 17920.3 CAPSS Report, Here Today – Here Tomorrow: The Road to Earthquake Resilience in San Francisco, Post-Earthquake Repair and Retrofit Requirements (ATC-52-4 Report), - https://sfgov.org/sfc/sites/default/files/ESIP/FileCenter/Documents/9761 atc524_compressed.pdf CUREE EDA-2: General Guidelines for the Assessment and Repair of Earthquake Damage in Residential Woodframe Buildings FEMA 306: Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings: Basic Procedures Manual

DISCUSSION :

San Francisco Existing Building Code, Section 405.2.3 triggers seismic evaluation, and possibly retrofit of buildings, when earthquake-related damage reaches the level of “substantial structural damage to vertical elements of the lateral-force-resisting system.” Substantial structural damage is defined in San Francisco Existing Building Code, Section 202 as, in essence, a loss of lateral capacity of 20 percent or more in any horizontal direction. The code does not give specific rules for identifying a 20-percent capacity loss nor guidance as to how to calculate capacity loss, so implementation of these code provisions relies on

interpretation by the Department of Building Inspection. This Bulletin presents the Department’s interpretation of a 20-percent lateral capacity loss based on visual indicators of such damage, and details the evaluation procedure and retrofit scope for buildings that exhibit earthquake-induced substantial structural damage. The Bulletin also provides guidance on the scope of required repair of building components or assemblies if such retrofits are not triggered.

In addition to substantial structural damage, San Francisco Existing Building Code, Section 405.2.2 triggers structural evaluation and possibly retrofit when earthquake-related damage reaches the level of disproportionate damage, which is defined in San Francisco Existing Building Code, Section 202 as, in essence, a lateral capacity loss of 10 percent or more in an earthquake of limited intensity. This Bulletin presents the Department of Building Inspection’s interpretation of a 10 percent capacity loss based on visual indicators of such damage and provides evaluation procedures and retrofit scope for buildings with such earthquake induced disproportionate damage.

Residential buildings that incur substantial structural damage or disproportionate damage as detailed in this Bulletin are considered to be “substandard” per California Health and Safety Code Section 17920.3(b) Structural hazards and (o) Inadequate structural resistance to horizontal forces.

APPLICABILITY

A building is eligible to apply the interpretations and provisions of this Bulletin if all of the following criteria are met:

A. The building includes at least one story in which the seismic force-resisting system consists of a wood lightframe system in at least one direction, and

• B. The building has only wood floor and roof diaphragms, and

C. The building contains a residential occupancy group R-3 as defined in San Francisco Building Code, Section

310. At the discretion of the Department of Building Inspection, a building in this group may be evaluated and repaired or retrofitted using the criteria for a residential building with three or more units under AB-098 if the building is structurally and architecturally similar to that group of buildings.

Buildings of other construction types and occupancies may also apply the provisions of this Bulletin on a case-by-case basis when approved by the Department of Building Inspection. Other methods of determining capacity loss based on analysis, testing, or other objective data may also be allowed at the discretion of the Department.

Qualified buildings may be permitted to be evaluated or retrofitted using the provisions in the California Historical Building Code provided that such provisions do not result in seismic performance that is less than the evaluation and retrofit engineering provisions detailed in this Bulletin.

For the purpose of determining if a building has incurred substantial structural damage or disproportionate damage per San Francisco Building Code, visual observation and classification of damage and severity may be used in lieu of a calculation of percentage loss of capacity. All determinations of substantial structural damage or disproportionate damage, including visual observation and classification of damage and severity, shall be made by a licensed design professional, and evaluation shall be submitted in accordance with San Francisco Existing Building Code, Section 405.2.3.1. For damage not deemed to be either substantial structural damage or disproportionate damage, repairs shall restore the building to its original strength or condition by methods acceptable to the Department of Building Inspection.

Earthquake-induced substantial structural damage to elements of lateral force-resisting system of a building shall be deemed to exist when any of the components and conditions is observed to reach the severity of “triggering damage” given in Table 1. For buildings with such substantial structural damage, evaluation and retrofit, where required, shall proceed in accordance with the “Action Required” column shown in Table 1 and the “Further Evaluation and Retrofit Engineering Criteria” section.

Disproportionate damage to elements of the lateral force-resisting system of a building shall be deemed to exist when any of the components and conditions is observed to reach the severity of “triggering damage” given in Table 1. For buildings with such disproportionate damage, evaluation and retrofit, where required, shall proceed in accordance with the “Action Required” column shown in Table 1 and the “Further Evaluation and Retrofit Engineering Criteria” section.

If, after an evaluation per San Francisco Existing Building Code, Section 405.2.3, the pre-earthquake building is determined to satisfy the criteria, then the building need not be retrofitted, but shall be restored to its pre-earthquake capacity. When retrofit is triggered by earthquake damage at any level, the engineering criteria for retrofit shall be permitted to use earthquake loads that are 75 percent of those prescribed by the San Francisco Building Code for new construction, in accordance with San Francisco Existing Building Code, Section 405.2.3.

Alternatively, any of the following codes, standards, or guidelines may be used as alternative evaluation or retrofit criteria for qualifying buildings:

• A. Meets the requirements of ASCE 31-03 for the Life Safety Performance Level, or

• B. Meets the requirements of ASCE 41-06 for the Life Safety Performance Level (S-3) in a BSE-1 earthquake hazard level, or

• C. Meets the requirements of CEBC Appendix A - Chapter A4 or IEBC Appendix A - Chapter A4 with NCSEA/SEAOC amendments, or

• D. Meets the San Francisco Existing Building Code, Sections 315, 320.

Originally Signed: Tom C. Hui, S.E. July 2, 2012 Acting Director Department of Building Inspection Approved by the Building Inspection Commission on 6/20/2012

NO. AB-105 : DATE : November 21, 2012 (Updated 01/01/2023 for code references) SUBJECT : Administrative Permit, Fire and Life Safety TITLE : Voluntary Sprinkler Protection for Existing High-Rise Buildings PURPOSE : The purpose of this Administrative Bulletin is to outline the procedure for documenting voluntary sprinkler protection of select high-rise buildings in DBI’s Permit Tracking System. It applies to existing high-rise buildings that (1) were built before State law required sprinkler protection in high-rise buildings (July 1, 1974) and (2) were excluded from San Francisco’s high-rise sprinkler retrofit ordinance (Ord. 377-93) and not required to comply with California Fire Code 1103.5.4. REFERENCES : Current edition of the San Francisco Existing Building Code - Section 314.27.1, General - Section 314.27.2, Additional requirements - Section 314.27.3, Permissible omissions Current edition of the San Francisco Fire Code - Section 903.2.15, Automatic sprinkler system–existing high-rise buildings DISCUSSION : San Francisco has many high-rise buildings that were built before the State required sprinkler protection in high-rise buildings. The City and County of San Francisco passed a high-rise sprinkler retrofit ordinance in 1993 (#377-93) to address this situation. This ordinance was codified in SFEBC Section 314.27. Basically, the ordinance required complete sprinkler protection in high-rise commercial buildings and tourist hotels built before the State law took effect. It also created a number of technical requirements specifically for high-rise buildings covered by the ordinance. It did not apply to pre-1974 high-rise residential buildings where occupants are primarily permanent in nature (currently classified as R-2 occupancies but classified as R-1 prior to 2008), mixed-use occupancies containing an R-1 or R-2 occupancy, or historic buildings. This Administrative Bulletin is intended to provide a mechanism for pre-1974 high-rise buildings to be recorded as fully sprinklered in DBI’s Permit Tracking System when they are voluntarily sprinklered throughout. It is similar to the process required for high-rise buildings covered by the ordinance but it is voluntary and more streamlined and culminates with an approved Administrative Permit rather than an approved “Umbrella Permit.”

The following criteria and procedures shall be followed to obtain an Administrative Permit for complete sprinkler protection of pre-1974 high-rise buildings exempted from the high-rise sprinkler ordinance.

A. Sprinkler Criteria

1. Schedule a pre-application meeting with SFFD to resolve applicable San Francisco requirements for the subject building. For example, the San Francisco Fire Code requires new high-rise buildings to have two fire pumps and two on-site water supplies for buildings over 200 feet high, fire department connections on each side of the building facing a street, and two risers per zone. These requirements may or may not be applicable, on a case-by-case basis, for existing pre-1974 high-rise buildings not covered by the ordinance.

2. For buildings that do not have any sprinkler protection, the new sprinkler system shall be designed and installed in accordance with the applicable edition of NFPA 13 in effect when the sprinkler permit application is submitted.

3. For buildings that are partially sprinklered, the existing sprinkler systems can remain as-is provided (a) the existing sprinkler systems have been maintained, (b) they are zoned on a per floor basis, and (c) the applicable sprinkler permits can be located in DBI’s files. If any of these provisions are not met, the appropriate resolution shall be determined through a pre-application meeting with DBI and SFFD. If any portion of the building is not sprinklered, the new sprinkler system shall be designed and installed in accordance with the applicable edition of NFPA 13 in effect when the sprinkler permit application is submitted.

4. For buildings that are believed to be fully sprinklered, proceed to sprinkler special inspection.

• B. Sprinkler Special Inspection

1. The building owner/manager shall engage a fire protection engineer to perform a sprinkler special inspection of the building and prepare a Sprinkler Special Inspection Report. The fire protection engineer shall be licensed in the State of California.

2. The sprinkler special inspector shall review DBI’s files to identify previous sprinkler permits for the subject building.

3. The sprinkler special inspector shall walk the entire building to verify complete coverage.

4. If the building does not have sprinklers in some areas, these deficiencies shall be transmitted to the building owner/manager and corrected by a licensed sprinkler contractor before the Administrative Permit application and Sprinkler Special Inspection Report are submitted for review and approval.

5. If the building does not comply with applicable requirements from the San Francisco Fire Code as determined by the pre-application meeting with SFFD (See A.1 above), these deficiencies shall be transmitted to the building owner/manager and corrected by a licensed sprinkler contractor before the Administrative Permit application and Sprinkler Special Inspection Report are submitted for review and approval.

6. For buildings that are completely sprinklered and comply with applicable San Francisco requirements, proceed to Sprinkler Special Inspection Report.

• C. Sprinkler Special Inspection Report

1. The sprinkler special inspector shall prepare a Sprinkler Special Inspection Report to be submitted with the Administrative Permit application.

2. The Sprinkler Special Inspection Report shall include the block and lot numbers, a brief description of the building, a table listing all sprinkler permits for the building including the sprinkler permit for correcting observed deficiencies, if any, and a statement that the building is fully sprinklered. If any sprinkler permits are still open, they must be closed before the Sprinkler Special Inspection Report is submitted for review and approval.

3. The report must be signed and stamped by the sprinkler special inspector.

• D. Administrative Permit Application

1. A standard building permit application and two copies of the Sprinkler Special Inspection Report shall be presented to Initial Permit Review (IPR). The submitter shall clearly state on the form that it is an Administrative Permit to document complete sprinkler protection. There is no construction so the value of construction on the form is $1.00.

2. After receiving a permit application number, the submitter shall hand-carry the permit application and Sprinkler Special Inspection Reports to DBI and SFFD stations for approval signatures.

3. After receiving all approval signatures and paying all permit fees, a Job Card and approved permit including a copy of the approved Sprinkler Special Inspection Report will be issued.

4. Inspection requests shall be made and final signatures obtained on the Job Card from the SFFD and subsequently from the DBI Building Inspector.

Whenever future renovations are made to an existing high-rise building which has an Administrative Permit confirming complete sprinkler protection, the approved Administrative Permit application number shall be clearly indicated on the permit application for renovations.

Signed by:

Tom C. Hui, S.E. November 21, 2012

Acting Director Department of Building Inspection Approved by the Building Inspection Commission on 11/21/2012

This bulletin provides information about procedures for administration of the Mandatory Seismic Retrofit Program for Wood-Frame Buildings. Detailed technical criteria and related information regarding this upgrade program for woodframe buildings may be found in Administrative Bulletin AB-107, Application of Engineering Criteria in SFEBC Chapter 5E .

The requirements of SFEBC Chapter 5E and the related design criteria represent a minimum standard to reduce earthquake risk. Property owners may undertake seismic retrofit improvements that exceed the requirements of SFEBC Chapter 5E.

Screening Form

On September 15, 2013, the Department will mail a Notice and Screening Form to all owners of buildings that are within the scope of SFEBC Chapter 5E. The Screening Form provides a simplified mechanism to determine if buildings must comply with the seismic upgrade requirements of SFEBC Chapter 5E, and to identify the time frame for building retrofit within a four-tier system. All Screening Forms must be returned to the Department no later than

September 15, 2014. Information provided on the Screening Form will be spot-checked by DBI staff; if errors are found or if additional information is required, the Department will contact the property owner or the owner’s designated representative.

Copies of the Screening Form and detailed instructions for completion and submittal of this form are available from the Department’s website at www.sfdbi.org/softstory or at the Department offices at 49 South Van Ness Avenue, San Francisco. There is no fee for submittal of the Screening Form.

A building that has been previously seismically upgraded or which the owner believes may already meet the requirements of SFEBC Chapter 5E may be exempt from this program if an evaluation confirms that the criteria detailed in SFEBC Chapter 5E are met. This confirmation may be done using the Optional Evaluation Form process. These forms and detailed instructions for completion and submittal of the form are available on the Department’s website at www.sfdbi.org/softstory or at the Department offices at 49 South Van Ness Avenue, San Francisco. A fee for a minimum of two hours of plan review time is due upon submittal of the Optional Evaluation Form. Additional fees may apply if more than two hours is required for plan review.

Building permit applications that are submitted to comply with this program will be reviewed for compliance with acceptable methodologies and appropriate design criteria. Insofar as possible, such review will be done over-thecounter. If over-the-counter review is not an available option, permit applications must be submitted. Such applications will be routed and tracked in accordance with standard Department procedures.

Plan review by other agencies

Review by agencies other than the Department of Building Inspection shall be in accordance with the guidelines set forth by the corresponding department . Where such guidelines do not cover specific issues or concerns, such other agencies will apply their standard plan review guidelines.

Fees for plan review and permit issuance by all agencies shall be as detailed in codes and regulations. Specific conditions of approval may be part of permit approval by any City agency. Project sponsors should carefully review all comments and notes on plans and permits regarding such conditions of approval.

In accordance with the specific requirements of the San Francisco Building Code, smoke detectors and carbon monoxide detectors may be required to be installed in a building at the time of this seismic upgrade work. Other work, such as water heater bracing, may also be triggered. Please review the codes and plan review comments for more information about such triggered such work.

In accordance with San Francisco Building Code Chapter 11B, Accessibility to Public Buildings, Public

Accommodations, Commercial Buildings and Public Housing, disability access improvements will be required when seismic upgrade work involves alterations and/or structural repairs. Chapter 11A, Housing Accessibility, may apply in certain unusual cases when a building has undergone a change of use, addition, or provides certain public or common use areas. A design professional or consultant will be able to provide guidance as to the scope of any such required disability access work.

Any proposal for seismic retrofit work that does not meet the specific technical requirements or the performance criteria detailed in SFEBC Chapter 5E , in Administrative Bulletin AB-107, or in this administrative bulletin may be considered for administrative approval by the Department of Building Inspection on a case-by-case basis if the requirements of San Francisco Building Code, Section 104A.2.8, Alternate Materials, Design, and Methods of Construction , are met. Such equivalencies or alternatives must be shown to be at least equal to the code requirements and criteria for structural integrity, suitability, strength, effectiveness, durability and safety. Applications for

modifications, equivalencies, or alternates should be submitted in accordance with the requirements of Administrative Bulletin AB-005, Procedures for Approval of Local Equivalencies.

Work undertaken to comply with SFEBC Chapter 5E must meet all requirements of the San Francisco Building Code including inspections and, when necessary, Special Inspections. Please review approved permits and permit documents regarding any such special inspection requirements.

Completion of Work

Completion of this required seismic upgrade work will result in the issuance of a Certificate of Final Completion (CFC). This CFC will be issued only following final inspection, submittal and approval of any Special Inspection documents, and compliance with all conditions of approval. The CFC document will become part of the permanent record of the building.

Extensions of time to complete work may be granted in accordance with SFBC Section 106A4.4, but such extensions may not extend the time beyond the deadline designated in SFEBC Table 5E-A for completion of required work.

Buildings that qualify to use the California Historical Building Code may apply the provisions and analysis techniques referenced in the California Historical Building Code, Chapter 8-7, Structural Regulations, and Chapter 8-8, Archaic Materials and Methods of Construction, and other provisions of that code upon approval of the Department. To determine if a building can be qualified to use the California Historical Building Code, please contact the Technical Services Division of the Department of Building Inspection at techq@sfgov.org.

Building owners are encouraged to provide earthquake recording instrumentation in their buildings. This instrumentation will typically require installation of sensors at the ground level, on the second floor, and at the highest story of a building. Costs of providing instrumentation are modest. The Department may assist in installation and maintenance of earthquake recording instruments in accordance with San Francisco Building Code , Section 1604.11. Earthquake recording instrumentation provides information about actual building movement. Instrumentation may be valuable to a building owner in providing a clearer understanding of actual building performance in an earthquake, possibly reducing the need for more detailed post-earthquake inspection and evaluation. The information from instrumented buildings will also provide scientists and engineers with a better understanding of the earthquake behavior of buildings. For information about participation in the optional earthquake recording instrumentation program, please contact the Technical Services Division at techq@sfgov.org.

Enforcement and abatement action will be promptly taken by the Department if a property owner fails to comply with any of the requirements of this program, including failure to submit a properly competed Screening Form or other document within the allowable one-year time, submittal of Screening Form or other documents that are found to contain errors or misrepresentations, failure to obtain a building permit or failure to complete all work and obtain a final inspection within the time limits indicated in SFEBC Table 5E-A, or for any other violation of this code. Such enforcement and abatement action will be in accordance with the requirements of San Francisco Building Code, Section 102A, Unsafe Buildings, Structures or Property.

In every case, when any required action has not been properly completed within the time limits of SFEBC Chapter 5E, the Department will post the building with a notice stating:

This building is in violation of the requirements ofthe San Francisco Building Code regarding earthquake safety.

This notice may not be removed until the building is in compliance with the requirements of SFEBC Chapter 5E. The notice shall also be recorded against the title of the property, with a release of this notice filed upon compliance with the requirements of SFEBC Chapter 5E.

Violation of any code requirement related to the upgrade of these buildings may subject the property owner to penalties detailed in San Francisco Building Code , Section 103A, Violations, including fines of up to $500 per day per violation and other penalties.

Board of Examiners

In cases where proposed modifications, equivalencies, or alternates substantially differ from those prescribed in this bulletin, such proposals may be referred by the Department to the Board of Examiners. Determinations made by the Department regarding technical provisions may be appealed by the permit applicant to the Board of Examiners in accordance with San Francisco Building Code, Section 105A.

Building Inspection Commission

Any person may appeal a determination of the Director related to these requirements to the Building Inspection Commission, pursuant to Chapter 77 of the San Francisco Administrative Code.

A list of buildings by street address and by block and lot number to which notice has been given regarding this required seismic upgrade program will be maintained and made public on the Department’s website. The Department will track the status of all buildings noticed under this program and will provide an annual update to the Mayor and the Board of Supervisors regarding the status of compliance. Originally Signed:

Tom C. Hui, S.E., C.B.O., September 27, 2013

Acting Director

Department of Building Inspection

Approved by Building Inspection Commission on September 18, 2013 Attachment A Wood-Frame Seismic Retrofit Program: Screening Form

Attachment B Wood-Frame Seismic Retrofit Program: Screening Form Instructions

Attachment C Wood-Frame Seismic Retrofit Program: Optional Evaluation Form

FEMA P-807, Seismic Evaluation and Retrofit of Multi-Unit Wood-Frame Buildings with Weak First Stories Administrative Bulletin AB-106, Procedures for Implementation of SFEBC Chapter 5E ABK, 1981, “Methodology for Mitigation of Seismic Hazards in Existing Unreinforced Masonry Buildings: Diaphragm Testing [Topical Report 03],” ABK, A Joint Venture, El Segundo, California, December. ANSI/AWC 2021 Special Design Provisions for Wind and Seismic Countryman, D., 1952. “Lateral Tests on Plywood Sheathed Diaphragms [Laboratory Report Number 55],” Douglas Fir Plywood Association, March 28, Information reaffirmed August 1963 . Countryman, D. and Colbenson, P., 1955. “1954 Horizontal Plywood Diaphragm Tests [Laboratory Report 63a],” Douglas Fir Plywood Association, January 25. NDS 05 Table 11E SEAOC Blue Book – Seismic Design Recommendations “Anchor Bolts in Light-Frame Construction at Small Edge Distances” ASTM E488/E488M-22 “Standard Test Methods for Strength of Anchors in Concrete Elements” DISCUSSION : SFEBC Chapter 5E, created with Ordinance 66-13, mandates the seismic retrofit of certain wood-frame residential buildings. Section 506E.2 allows different criteria, or compliance alternatives. Section 506E.4 calls for the development and publication of this Administrative Bulletin to “detail the technical requirements to be used for the evaluation and retrofitting of buildings required to meet the criteria established in Section 506E.2.” SCOPE : This bulletin covers only SFEBC Sections 506E.2 through 506E.4. AB-106 covers administrative and procedural requirements of Chapter 5E. This Bulletin is separate from, but intended to be in coordination with, other sections of Chapter 5E, other Administrative Bulletins, and other forms and instructions. Part A of this Bulletin applies to all projects seeking to comply with Chapter 5E, regardless of the compliance alternative. Parts B through G apply, respectively, to the specific compliance alternatives allowed in Section 506E.2.

DEFINITIONS: In addition to the definitions in Section 503E, the following definitions shall apply for purposes of this Bulletin:

TARGET STORY. Any story above grade plane, or any basement or underfloor space that extends above grade at any point, in which the wall layout or plan configuration is substantially different from the wall layout or plan

configuration in the story above, except that a story is not a Target Story if it is the topmost story or if the difference in configuration is primarily due to the story above being a penthouse, an attic with a pitched roof, or a setback story.

Commentary: This definition is taken from the Screening Form Instructions developed to implement Section 506E.2, but it has been modified to clarify that the consideration of “substantially different” wall layout or configuration applies to basements and underfloor areas as well as to stories above grade plane. As discussed in the Screening Form Instructions, “substantially different from” generally means “substantially weaker than” and can be a matter of engineering judgment, to be decided as part of the Screening Form approval process. As described in the Screening Form and Screening Form Instructions, Chapter 5E applies only to wood-frame target stories, that is, target stories in which the seismic force-resisting system in any direction relies on wood-frame wall elements. A building can have more than one target story.

A2.1. Site Class E. Buildings located in areas labeled “NEHRP E” on the latest USGS map of “Soil Type and Shaking Hazard in the San Francisco Bay Area” will be assigned to Site Class E unless site-specific investigation in accordance with ASCE 7-16 Chapter 20 indicates otherwise.

A2.2. Site Class F. The requirement in ASCE 7-16 Section 11.4.8 for site response analysis of Site Class F sites is waived, such sites should be considered as Site Class E.

Commentary: SFEBC Chapter 5E does not require mitigation of existing geologic site hazards such as liquefiable soil. Also, many buildings subject to Chapter 5E would be exempt from site response analysis by the exception to ASCE 7-16 Section 20.3.1.

A2.3. Seismic ground motion values. Where seismic ground motion values are calculated per ASCE 7-16 Section 11.4 or by similar provisions, the value of Fa shall be taken as 1.3 for Site Class E.

Commentary: This requirement applies to any code-based procedure for calculating seismicity parameters, such as that used by CEBC Appendix A - Chapter A4 and application of “regular code” provisions through the California Historical Building Code. It also applies where criteria such as ASCE 31, ASCE 41, and FEMA P-807 apply equations similar to those in ASCE 7 Section 11.4. When using the USGS ground motion application, engineers are cautioned to confirm use of the correct value Fa as described above.

A3.1. Building investigation and report. In support of an engineering evaluation or retrofit design, the owner shall conduct or cause to be conducted an investigation of the existing building. The engineer of record shall prepare a written report documenting procedures, findings, and conclusions of the investigation. The report may reference other materials submitted to demonstrate compliance or to support findings and conclusions.

A3.1.1. Scope of investigation. At minimum, the investigation shall comply with any investigation and assessment provisions in the engineering criteria selected from SFEBC Section 506E.2, as modified by subsequent Parts of this Bulletin. Otherwise, the investigation scope and methods may generally be set at the discretion of the engineer of record, but all findings shall be reported. The Department is authorized to require additional investigation as needed to fulfill the purpose of the report and the intent of SFEBC Chapter 5E. With the approval of the Department, field verification of assumed conditions may be performed during the construction phase.

As needed or required, the investigation shall include identification, verification, and assessment of existing conditions relevant to the engineering assumptions applied in the evaluation or retrofit design. The investigation shall be based on a combination of non-destructive testing or inspection, destructive testing or inspection, and reference to record documents. Where record documents are used to reduce the scope of testing or other on-site work, appropriate field verification is required.

Commentary: With respect to evaluation, the primary purpose of the investigation is to identify or confirm the nature of the existing construction as needed to justify load drift curves, tributary floor weights, load path assumptions, etc. A secondary purpose is to

provide condition assessment sufficient to rule out deterioration or construction defects significant enough to affect earthquake performance of the structure as a whole. The investigation should therefore seek evidence of damage, deterioration, or defective construction sufficient to affect significantly the performance of the seismic force-resisting system. With respect to retrofit design, the primary purpose of the investigation is to confirm design assumptions regarding the adequacy of existing seismic load path components within the context of the retrofitted structure. In addition, though it need not be stated in the provision, the Department is always authorized to require repair of damage, correction of defects, and elimination of dangerous conditions; hence the requirement that “all findings shall be reported.”

A3.1.2. Timing of investigation. Unless otherwise required by the engineering criteria selected from SFEBC Section 506E.2, as modified by subsequent Parts of this Bulletin, with the approval of the Department, investigation may be deferred to a confirmation or construction phase. The deferred investigation shall be specified as a special inspection item in accordance with SFBC Chapter 17.

Commentary: This allowance is offered for the benefit of owners for cases in which destructive investigation will be unusually disruptive or expensive. However, the owner will bear the risk of change orders, design revisions, and supplemental design review if actual conditions differ from those assumed by the evaluation or design. Approval of the Department is required to allow the Department to identify cases where deferred investigation will complicate its review and approval process. The Department may allow some parts of the investigation to be delayed while requiring other parts of the investigation to be completed prior to review of calculations.

A3.2. Existing materials and components. Where the applicable engineering criteria specify material or structural properties of existing elements, those criteria shall be used. Otherwise, the general rules of this section apply. A3.2.1. Damage and defects. The capacity of any element damaged by deterioration, wear, or other causes or constructed or altered so as to differ from its intended condition shall be reduced based on the judgment of the engineer of record, subject to review of condition assessment findings and the approval of the Department. This provision shall apply where the applicable engineering criteria do not make an explicit provision for capacity reduction.

Commentary: This provision is consistent with ASCE 31-03 Section 4.2.4.4.

A3.2.2. Relation of nominal and expected strength to allowable stress. Where element capacities are based on allowable stresses from codes and standards, nominal strengths shall be taken no greater than the allowable stresses multiplied by the following factors: 1.7 for steel; 2.5 for masonry; 2.0 for wood. Where the element is ductile or deformation-controlled, the expected strength shall be taken as 1.25 times the nominal strength.

Commentary: This provision is consistent with ASCE 31-03 Section 4.2.4.4.

A3.2.3. Concrete footings and stem walls. Evaluation and design of existing concrete footings shall be permitted to assume default concrete strength based on ASCE 41-13.

A3.2.4. Unreinforced brick footings. The capacity of an existing brick footing to resist shear or pullout of an existing or new anchor shall be established by testing or by reference to approved tests of similar conditions. Where the capacity of an anchor is limited by failure of the footing or grout, the anchored wall or frame element shall be considered non-ductile or force-controlled.

Commentary: Because FEMA P-807 presumes ductile retrofit elements, the last sentence of this provision means that retrofit elements designed with FEMA P-807 may only be used with brick footings when testing has demonstrated that the anchor will develop the strength of the wall or frame element or will yield itself in a ductile fashion.

Reserved.

A3.2.6. Sheathed wood-frame walls and partitions. Wood-frame walls and partitions shall be permitted to use peak strength values from Bulletin Section B5.1.1. Where these values are used, they shall be taken as expected strengths and reduced to nominal strength per Bulletin Section A3.2.2 where used on non-ductile or force-controlled elements. This provision is subject to the following limitations:

1. A wall assembly may be considered deformation-controlled if all sheathing materials that are individually forcecontrolled are ignored in the strength calculation.

2. Retrofit designs based on R values from the building code shall use only code-approved sheathing materials and combinations appropriate to the assumed R value.

Sill plates of all walls that are considered to resist seismic shear forces shall be anchored to the foundation, structural slab or stem walls that they rest on. Total shear capacity of competent existing bolts and any added anchor bolts shall be adequate to resist the shear demand on the wall. Anchors in walls that are not considered to resist seismic shear forces are not required to be investigated.

When investigation confirms the presence of concrete foundations supporting 2x or 3x sill plates anchored with ½" to ¾" diameter bolts with washers and nuts, it is acceptable to determine in-plane shear capacities in accordance with applicable tables in ANSI/AWC National Design Specification, provided that the supporting concrete is sound, sill plates are in good condition, anchor bolts do not show extensive corrosion, and anchors are located in the concrete per SFBC Section 1905.

The capacity of existing sill plate anchors in brick footings or stem walls shall be established per Section A3.2.4. Maximum spacing between existing sill plate anchor bolts shall be six (6) feet for walls with plywood sheathing and ten (10) feet for other shear walls (archaic walls). There shall be a minimum of two (2) shear anchors per each wall segment that is considered to resist seismic forces.

All anchors for which capacity cannot be determined by calculation, or for which capacities are not published in an approved Standard, may have capacities established by testing. Anchor bolts that are placed out of plumb, are loose, show extensive signs of corrosion, or are otherwise damaged shall not be considered to provide lateral load resistance. Where new anchors are required, strength, spacing and installation requirements shall be determined in accordance with the SFBC.

Commentary: Reliable performance of a lateral load resisting system depends on the presence of a complete load path, from floor diaphragm through the lateral load resisting elements and their foundation, to the supporting soils. Absence of an adequate connection between the wood sill and foundation is a gap in the load path that limits the ability of the shear wall to resist seismic forces.

A3.2.8. Default strength values for diaphragms. Default values for evaluation and retrofit design of existing or strengthened diaphragms may be taken from ASCE 41-13 Table 12-2 or 15-2 when using ASCE 31 or ASCE 41, or from SDPWS-08 Tables 4.2A through 4.2D (AF&PA, 2009) when using CEBC Appendix A- Chapter A4, with adjustments for nominal v. expected strength, ASD, or LRFD. When using FEMA P-807, diaphragm strength may be determined using the nominal strength from ASCE 41 or SDPWS multiplied by phi = 1.0, or peak expected strength as provided in Table A3.2.8.

Table A3.2.8 Peak Expected Strength of Existing or Strengthened Horizontal Diaphragms for use with FEMA P-807.

Diaphragm Description Peak Expected Strength (plf)

1 Case refers to load case diagrams in SDPWS Table 4.2A

Commentary: This section identifies sources of diaphragm capacities suitable where Chapter 5E requires diaphragm evaluation or strengthening. Table A3.2.8-1 is for use only with procedures like FEMA P-807 in which capacities are based on estimated peak strength. Because FEMA P-807 is based on the estimated peak strength of vertical elements, the diaphragm strength is allowed to be derived on a similar bases, with a phi factor of 1.0. Expected strengths in Table A3.2.8-8 are based on test information from APA (Countryman, 1952; Countryman and Colbenson, 1955) and ABK (1981). Reference to SDPWS in the table is only for load case diagrams; expected strengths are to be taken from the table.

A4.1. Submittals. Structural calculations and supporting documents shall be prepared and submitted as required by Bulletin Section A4.2. Other documents shall be prepared and submitted as required by Administrative Bulletin 106. A4.2. Structural calculations and supporting documents. Structural calculations shall be submitted as required to confirm compliance with the selected engineering criteria. Calculations shall be specific to the engineering criteria used and shall include, at minimum:

1. A statement that the evaluation or retrofit design was prepared to demonstrate compliance with SFEBC Chapter 5E.

2. Identification of the engineering criteria used for the evaluation or retrofit design, including the performance objective used with FEMA P-807, ASCE 41-06, or ASCE 41-13.

3. All building investigation, soils, geotechnical, or other supporting reports, as well as a summary of such reports indicating how the findings or conclusions are reflected in the structural calculations.

4. Identification of structural properties and capacities assumed for all existing materials and elements, including any capacity reductions for damage, deterioration, or defect.

5. Identification of structural properties and capacities assumed for all new materials and elements, including product literature for proprietary devices.

6. If requested by the Department, verification calculations for any engineering software used.

7. Other information as required by the Department.

A5.1. Testing and inspection. All work shall comply with inspection and testing requirements of the building code as they apply to existing buildings and structures. Additional field verification, structural observation, testing, and inspection may be required in accordance with the selected engineering criteria or as directed by the Department. A6.1. Use of Steel Special Moment Frames. Special Steel Moment Frames shall comply with all applicable provisions of AISC 341-10, including but not limited to connection design and lateral bracing of beams. Exception: The “strong-column/weak-beam” provision of AISC 341-16, Section E3.4a is waived, provided that the columns carry no gravity load.

It is permitted to employ approved commercially available proprietary frame systems to achieve the Special Moment Frame classification.

Chapter A4 allows the use of any seismic force resisting system permitted in the building code, when the applicable R factor is employed. The building code (through reference to ASCE7) permits the use of steel moment frames other than Steel Special Moment Frames in light frame construction only when specific limitations regarding the building height and unit weights of floors and walls are met. These limitations are waived for buildings with no more than three stories above the highest Target Story. The R , Ω 0 , and Cd factors employed shall be those applicable to the selected

A6.3. Use of Cantilevered Column Systems. Cantilevered column systems conforming to the following provisions may be considered as moment frame systems (Special, Intermediate, or Ordinary, as applicable, based on detailing) with regard to determination of the R , Ω 0 , and Cd factors.

1. Columns shall not carry gravity load.

2. Columns shall be configured in pairs (or larger groups) connected by a continuous foundation or grade beam.

3. The continuous foundation or grade beam shall be designed to resist the expected plastic moment at the base of each column, computed as RyFyZ , as defined in AISC 341-16.

4. The flexibility of the continuous foundation or grade beam, considering cracked section properties of reinforced concrete, shall be included in computing the deformation of the cantilevered column system.

5. Cantilevered columns shall be considered as twice their actual height when checking lateral torsional buckling.

B1.1. Performance Objective

B1.1.1. Hazard level. The spectral demand shall be 0.5 SMS , calculated in accordance with ASCE 7-16 Section 11.4 except that for sites in Site Class E, the value of Fa shall be taken as 1.3.

Commentary: The value of Fa is modified for Site Class E to adjust the demand for site effects not considered explicitly in the development of FEMA P-807 (see FEMA P-807 section 2.6.1).

B1.1.2. Performance level. Acceptable performance shall be based on drifts corresponding to the Onset of Strength Loss in the seismic force-resisting wood-frame elements.

Commentary: This provision merely reflects the requirements of the ordinance, referencing the Onset of Strength Loss performance level defined in FEMA P-807. It does not require any additional work by the engineer, since the Onset of Strength Loss criteria are already embedded in the criteria given in this Bulletin.

B1.1.3. Maximum drift limit probability of exceedance. The maximum drift limit POE for evaluation or retrofit design shall be 30 percent.

Exception: Where the story or underfloor area subject to evaluation or retrofit contains only parking, storage, or utility uses or occupancies, the maximum drift limit POE for evaluation or for retrofit design shall be 50 percent, as long as the additional requirements of Bulletin Section B7.3 are met.

Commentary: This Exception incorporates the alternative criteria given in SFEBC Section 506E.3. The alternative criteria apply to what FEMA P-807 calls “optimized retrofit,” as discussed in FEMA P-807 Sections 6.3.1 and 6.4.2.

B1.2. Required scope of work. Compliance with the provisions of SFEBC Chapter 5E using FEMA P-807 requires:

1. Correction of all aspects of eligibility non-compliance per Bulletin Section B3, and

2. Correction of all building survey non-compliance per Bulletin Section B4, and either

• 3a. Demonstration of an acceptable existing condition per Bulletin Section B6, or

Where retrofit is required but the provisions of Bulletin Section B7 cannot be satisfied, the building shall be

considered ineligible for compliance with SFEBC Chapter 5E using FEMA P-807.

Commentary: In some instances, the notation and terminology differ slightly from those in FEMA P-807 Chapters 1-7.

B2.1. Terminology. Terms used in Bulletin Part B shall have the meanings provided here. Terms not defined here shall have the meanings provided in the building code.

CENTER OF STRENGTH. At each story, the location in plan that represents the weighted average location of the load in all wall lines, at the drift associated with the story strength.

DRIFT. For a given story, the calculated or postulated lateral deflection within that story divided by the story height, normally expressed as a percentage.

FIRST STORY. Any target story subject to SFEBC Chapter 5E .

LOAD-DRIFT CURVE. For a wall assembly, wall line, or story, the relationship characterizing the variation of shear resistance versus drift, for the full range of relevant drifts. For a wall assembly, the load value is given in units of force per unit length. For wall lines and stories, the load value is given in units of force.

LOAD-ROTATION CURVE. For a story, the relationship characterizing the variation of torsional resistance versus story rotation, for the full range of relevant rotations, given in units of torque as a function of rotation angle.

PROBABILITY OF EXCEEDANCE (POE). The desired or calculated probability that the structure will respond beyond the drift limits representing the desired performance level, in at least one direction, when subjected to a specified hazard level. Within SFEBC Chapter 5E and this Bulletin, POE means the probability of exceeding the drift limits associated with Onset of Strength Loss.

Commentary: As used in SFEBC Chapter 5E and this Bulletin, POE is identical to what FEMA P-807 Chapters 1 through 7 typically call “drift limit POE.”

QUALIFYING WALL LINE. For purposes of checking eligibility of floor or roof diaphragms, a wall line that contributes substantially to the peak story strength and has an adequate load path connecting it to the diaphragms it affects.

Commentary: See FEMA P-807 Section 2.6.4 for discussion of rules for “qualifying” wall lines. The definition is subject to the judgment of the engineer of record and the Department.

SPECTRAL CAPACITY. For a given POE, the highest level of spectral acceleration a structure can sustain without responding beyond the drift limits representing the desired performance level, given as a multiple of the acceleration of gravity, and calculated separately in each principal direction.

SPECTRAL DEMAND. See Bulletin Section B1.1.1. The spectral demand is given as a multiple of the acceleration of gravity.

STORY. For purposes of applying engineering criteria in SFEBC Section 506E and this Bulletin, see the building code definition and this Bulletin’s definition of First Story. The definition in SFEBC Section 503E applies only to the counting of stories for determining scope per SFEBC Section 502E.

STORY STRENGTH. The maximum load value from the story load-drift curve, calculated separately in each principal direction.

STORY STRENGTH, BASE-NORMALIZED. The story strength divided by the total seismic weight of the building. STORY STRENGTH, STORY-NORMALIZED. The story strength divided by the sum of the tributary floor weights of all the floors above the story in question.

STORY TORSIONAL STRENGTH. The maximum torsional resistance value from the story load-rotation curve. STRENGTH DEGRADATION RATIO. In each direction, a value between 0.0 and 1.0 calculated as the first story strength divided by the load corresponding to a drift of 3 percent from the first story load-drift curve.

TORSION COEFFICIENT. A value that need not be taken greater than 1.4, calculated as the first story torsional demand divided by the first story torsional strength.

TORSIONAL ECCENTRICITY. The absolute value of the plan distance, in x and y components, between the second story center of strength and the first story center of strength.

TRIBUTARY FLOOR WEIGHT. The total seismically active weight tributary to a single floor level comprising dead load and applicable live load, snow weight, and other loads as required by the building code. UPPER STORY. Any story above the first story.

WALL ASSEMBLY. A unique combination of sheathing materials over wood-stud framing.

WALL LINE. A collection of full-height and partial-height wall segments or frames within a single story that satisfies the rules in Bulletin Section B5.1.2.

Commentary: A wood-frame wall line is generally assumed to contribute strength only in the direction parallel to its length. A wall line expected to contribute strength in a direction other than parallel to its length, such as a cantilever column or fixed-based moment frame, must be modeled appropriately.

WALL SEGMENT. A portion of wood-frame wall made from a single wall assembly. For purposes of this definition, any sheathed run of wood-stud framing that could contribute to a story’s lateral strength or stiffness shall be considered a potential wall segment, whether or not the framing and sheathing were intentionally designed, detailed, sized, or located to contribute that strength or stiffness.

AU The base-normalized upper-story strength, calculated separately for each direction.

AW The weak-story ratio, calculated separately for each direction.

CD The strength degradation ratio, calculated separately for each direction.

CT The torsion coefficient.

CU The minimum of the story-normalized story strengths of any of the upper stories, calculated separately for each direction.

Commentary: Where the story strength is roughly constant for all upper stories, CU will generally be the story-normalized strength of the second story.

COSi The plan location, in x and y coordinates, of the center of strength of story i .

• ex, ey The x and y components, respectively, of the torsional eccentricity.

• fw The load-drift curve for wall line w .

• Fi The load-drift curve for story i , calculated separately for each direction.

• hw The floor-to-ceiling height of wall line w .

• H1 The floor-to-ceiling height of the tallest first story wall line, determined separately in each direction.

• I A subscript index indicating floor or story. Story i is between floor i and floor i+1 .

• Lw The length of wall line w , taken as the longest possible length of wall that satisfies the rules in Bulletin Section

• B5.1.2, including the length of any openings within it.

• Lx The overall building dimension in the x direction.

• Ly The overall building dimension in the y direction.

• POE Probability of Exceedance

• Qopen The adjustment factor for openings in a wall line.

• Qot The adjustment factor for overturning of a wall line.

• Qs The story height factor for the first story, calculated separately for each principal direction.

• Sc The spectral capacity, calculated separately for each direction.

• Sd The spectral demand.

• ti The load-rotation curve for story i .

• Ti The story torsional strength of story i .

• V1r The story strength of the retrofitted first story, calculated separately for each direction.

• Vi The story strength of story i , calculated separately for each direction.

• VU The story strength of the upper story that determines the value of CU .

Commentary: Where the story strength is roughly constant for all upper stories, VU will generally be the second story strength.

• w A subscript index indicating a single wall line.

• W The total seismic weight of the building, equal to the sum of all the tributary floor weights.

• Wi The tributary floor weight of floor i .

• WSP Wood structural panel

• x A subscript index indicating one of two principal directions.

• α POE,0 The POE adjustment factor for a CD value of 0.0.

• α POE,1 The POE adjustment factor for a CD value of 1.0.

• δ Drifts at which load-drift curves are characterized. See Table B5.1.1. j

• Δ i In each direction, the drift at which the story strength of story i occurs.

• J 1 The first story torsional demand.

B3.1. General. Buildings that do not comply with the requirements of Bulletin Section B3 shall be considered ineligible for compliance using FEMA P-807.

Exception: Buildings in which all aspects of non-compliance will be eliminated through alteration or retrofit are eligible for compliance using FEMA P-807.

B3.2. Massing

1. The building has no more than four stories above grade plane at any point around its perimeter.

2. The building’s wood-framed stories are not supported by an above-grade podium structure.

Commentary: Item 1 relies on the building code’s definition of story above grade plane. Item 2 is referring to a concrete podium structure generally extending at least one story above grade and topped by a concrete diaphragm that provides a base for wood framing above. Item 2 is not intended to rule out concrete foundation elements or stem walls that extend above grade.

1. The upper-story seismic force-resisting systems are bearing wall or building frame systems of wood-frame walls with shear panels.

2. The upper-story floor-to-floor heights are between 8 feet and 12 feet and are constant within each story.

3. In each upper story, in each principal direction, the distance from the center of strength to the center of mass of the floor below it is no more than 25 percent of the corresponding building dimension.

Commentary: The intent of this approximate rule is to ensure that no upper story is prone to significant torsion, and that inertial forces from upper stories should transfer to the first story near the geometric center of the second floor. See FEMA P-807 Section 2.6.2.

4. No upper story or floor above an upper story has a weight irregularity as defined by ASCE/SEI 7-16 Table 12.3-2, Type 2.

5. No upper story has a vertical geometric irregularity as defined by ASCE/SEI 7-16 Table 12.3-2, Type 3.

1. The first story height may vary, but the maximum first story height, from top of foundation to top of second floor framing is between 8 feet and 15 feet.

2. The first story seismic force-resisting systems are bearing wall or building frame systems of wood-frame walls with shear panels or combine such systems with steel moment-resisting frame systems, steel cantilever column systems, or steel buckling-restrained braced frame systems.

Commentary: FEMA P-807 is not suitable for evaluating or designing concentrically braced frames, concrete shear walls, or reinforced masonry shear walls. See FEMA P-807 Section 6.5. If these systems exist or are proposed for as retrofit elements, compliance must be demonstrated using one of the other methods allowed by SFEBC Section 506E.2.

3. The first story includes no full-height concrete or masonry walls.

Commentary: Buildings with full-height concrete or masonry walls at the full perimeter of the story of interest are expected to be exempt from SFEBC Chapter 5E. Buildings with a combination of full-height concrete or masonry walls and other systems (woodframe walls, steel moment frames, etc.) might be required to comply with SFEBC Chapter 5E but will not be able to use FEMA P-807 to demonstrate compliance.

4. The first story walls and frames have continuous concrete footings or concrete slab-on-grade foundations. If some or all of the first floor is raised over a crawl space, the crawl space has concrete stem walls to the underside of the first floor framing.

Commentary: Concrete stem walls are considered to provide a base similar to a concrete foundation. Wood-framed cripple walls, whether braced or unbraced by sheathing of any type, are not adequate to meet this provision.

5. First story walls and frames may be partial height over a concrete or reinforced masonry retaining wall or foundation stem wall, but any partial-height wall or frame is at least four feet tall from top of stem wall to underside of second floor framing.

6. If the building has a basement, the basement walls and the floor diaphragm just above them are capable of transferring seismic forces between the foundation and the first story, and the basement story is laterally stronger than the first story above it.

B3.5. Floor and roof diaphragms. Floor and roof diaphragms shall satisfy the eligibility requirements of this subsection.

Exception: Diaphragms shown to have no deficiencies or irregularities that would prevent development of the strength of any seismic force-resisting wall or frame or would otherwise control the overall seismic response of the structure need not satisfy the eligibility requirements in this subsection.

Commentary: The intent of these approximate rules for diaphragms is to ensure that the structure does not develop a premature mechanism or failure mode. See FEMA P-807 Section 2.6.4 for additional explanation and guidance.

1. No portion of the second floor diaphragm between qualifying wall lines has an aspect ratio greater than 2:1.

2. The second floor diaphragm does not cantilever more than 25 feet from a qualifying wall line.

3. If the second floor diaphragm cantilevers more than 10 feet from a qualifying wall line, diaphragm chords are adequate to develop the lesser of the strength of the diaphragm or the diaphragm forces associated with the peak strength of the qualifying wall line.

4. No floor or roof diaphragm has a reentrant corner irregularity in which either projecting leg of the diaphragm beyond the reentrant corner is longer than 15 percent of the corresponding plan dimension of the building, unless each leg of the diaphragm satisfies the aspect ratio and cantilever rules of this subsection.

Commentary: This provision differs from the irregularity defined in ASCE/SEI 31-03 or as Type 2 in ASCE/SEI 7-16 Table 12.3-1 in order to limit diaphragm demands. See FEMA P-807 Section 2.6.4.

5. No floor or roof diaphragm has a vertical offset unless load path components are present and adequate to develop the diaphragm strength across the offset.

6. No floor or roof diaphragm has cutouts or openings within it such that, along any line across the diaphragm, the sum of the opening widths along that line is more than 25 percent of the overall diaphragm dimension along that line.

B4.1. General. Structural components shall be investigated in accordance with Bulletin Section B4 as needed to confirm eligibility per Bulletin Section B3 and to support structure characterization per Bulletin Section B5, evaluation per Bulletin Section B6, and retrofit design per Bulletin Section B7.

B4.2. Wall framing and sheathing. The investigation shall determine the length and location in plan of all wall segments and wall lines in all stories as needed to calculate load-drift curves.

The investigation shall determine the size and location of openings in each wall line as needed to calculate adjustment factors for openings and adjustment factors for overturning.

The investigation shall determine all unique frames or wall assemblies in the first story and representative wall assemblies in the upper stories. Where sheathing includes wood structural panels or where sheathing load-drift data is

a function of nailing, the investigation shall also determine the nail size and edge nail spacing. Panel edge nailing shall be investigated over at least five nail spaces and as needed to confirm a reliable spacing assumption.

Commentary: Unless building-specific conditions indicate a need for more extensive investigation, the minimum recommended investigation should include one location of each distinct wall assembly in the first story and in any upper story, but not less than one perimeter and one interior wall line in the first story and in any upper story. If prior investigation reports based on destructive investigation are available, they may be relied on. If original drawings are available, they may be relied on to reduce the scope of investigation, but some investigation is still necessary to confirm the reliability of the drawings.

B4.3. Floor and roof framing and diaphragm. The investigation shall determine the construction of floor and roof framing and diaphragm sheathing, including the direction of framing and the mechanism of gravity load transfer, as needed for calculation of adjustment factors for overturning. The second floor shall be investigated. Subject to approval of the Department, the roof and upper floors need not be investigated in detail where there is evidence that their relevant attributes are similar to those of the second floor.

B4.4. Load path components. The investigation shall determine the nature of the load path components and connections for transfer of forces between diaphragms and walls or frames as needed to confirm that the wall line will participate in resisting drift.

Commentary: For non-WSP sheathing, the intent is to confirm that fastening reasonably conforms to conventional construction requirements. For existing WSP shear walls with nail spacing closer than six inches, it should be confirmed at representative locations that shear wall top and bottom connection capacity is appropriate to the sheathing capacity.

The investigation shall determine the presence or absence of hold-down hardware at the base of all first story walls, as well as the adequacy of installation of representative types at representative locations.

The investigation shall confirm that anchors are provided at the base of the first story walls.

Table B4.4 shows where the load path may be assumed adequate or is subject to investigation or confirmation. Table B4.4 applies only to walls whose strength is counted in the analysis. For any condition subject to investigation, the load path may be assumed lacking, and the corresponding wall strength may be ignored, but only if assumed so consistently throughout the building.

Commentary: The load path may be assumed lacking, but not selectively so as to “correct” torsion or other irregularities. This provision is similar to ASCE 31 and ASCE 41 limits on the designation of secondary components.

Exception: Wherever the strength of two stories is being compared, an adequate load path must be assumed for all walls and partitions in the upper story.

Commentary: The exception prevents underestimating the upper story strength. The exception will apply for calculations of weak story or soft story ratio in ASCE 31/41, CEBC Appendix A - Chapter A4, and other code-based procedures; application of the 1.3 cap on retrofit strength for ASCE 41 and CEBC Appendix A - Chapter A4 retrofits; and calculation of spectral capacity with FEMA P-807.

The adequacy of an investigated load path may be confirmed by the judgment of the design professional, without calculations, but is subject to approval by the Department. Judgment should be based on the presence of a positive connection with multiple or redundant attachments distributed over the length of the wall line. For partitions perpendicular to floor framing above, blocking between floor joists nailed to the partition top plate (through a lath nailer, if present) should be deemed adequate for partitions with non-WSP sheathing.

Table B4.4. Investigation Requirements for Load Path between Partitions and Floor Framing Above

B4.5. Foundation elements. The investigation shall determine the nature of the existing foundation elements and supporting soils as needed for calculation of adjustment factors for overturning.

B5.1. Story strength

B5.1.1. Wall assemblies. For each wall assembly present, a load-drift curve shall be computed by summing contributions from Table B5.1.1 at each drift level for each layer of sheathing. With approval of the Department, test results specific to the wall assembly or its components may be used in place of Table B5.1.1.

Commentary: See FEMA P-807 Section 4.4 and Appendix F regarding the development of Table B5.1.1 and the use of alternate test data.

The values in Table B5.1.1 are subject to the following additional requirements:

1. Horizontal wood sheathing or wood siding shall be at least 1/2" thick and fastened to existing studs with at least two nails per board per stud. Otherwise, the expected strength shall be taken as 0.

2. Where siding panel edges are lapped, each panel shall be nailed separately. Otherwise, the expected strength shall be taken as 0.

B5.1.1.1. Wall assemblies without wood structural panel sheathing. The assembly load drift curve is the sum of the load drift curves for each of the sheathing layers.

B5.1.1.2. Wall assemblies with wood structural panel sheathing. The assembly load drift curve is whichever of the following two load-drift curves has the larger peak strength:

1. The assembly load-drift curve using 50 percent of the strength of the wood structural panel layers and 100 percent of the strength of the other sheathing materials.

2. The assembly load-drift curve using 100 percent of the strength of the wood structural panel layers and 50 percent of the strength of the other sheathing materials.

• B5.1.2. Wall line assignment. Each segment of sheathed wall framing within a story shall be assigned to a wall line. Wall lines shall satisfy the following rules:

1. Full-height wall segments separated by window or door openings but connected by sheathed segments and continuous framing above or below the opening shall be assigned to the same wall line, unless other rules require them to be treated separately.

2. Wall segments assigned to the same wall line shall not be offset out-of-plane from adjacent segments by more than four feet.

3. At bay windows, the wall segments within the common plane shall be assigned to the same wall line if they satisfy the other rules, but the wall segments within the cantilevered portions of the bay shall not be counted toward the wallline strength.

4. Wall segments of different heights, including wall segments along a stepped foundation, shall be assigned to separate wall lines.

5. A wall segment of varying height due to a sloped foundation shall be assigned to a separate wall line, and its height shall be taken as the average height of the segment.

6. Wall segments of different wall assemblies shall be assigned to separate wall lines.

7. Where hold-downs exist at each end of a wall segment, that segment may be considered a separate wall line.

8. Wall segments less than one foot long shall be treated as openings.

9. Wall segments between openings with height-to-length ratios greater than 8:1 shall be treated as openings.

10. Steel elements (moment frames, cantilever columns, etc.) shall be assigned to separate wall lines.

11. Wall segments or frames considered to have significant damage, deterioration, or construction defects may be counted toward a wall line’s strength but shall have their load-drift strength values reduced.

B5.1.3. Wall line load-drift curve. For each wall line, a load-drift curve shall be computed by multiplying the applicable wall assembly load-drift curve by the wall line’s length and by applicable adjustment factors per Bulletin Equation B5.1.3-1.

where:

fw is the load-drift curve of wall line w , expressed as a function of drift.

vw is the load-drift curve of the wall assembly associated with wall line w , as derived per Bulletin Section B5.1.1 and adjusted for height variation per Bulletin Section B5.1.3.1.

B5.1.3.1. Adjustment for height variation. Where first story wall lines in a given direction are of different heights, the load-drift curve of the wall assembly of each wood-frame wall line shall be adjusted to account for increased drift demands in all but the tallest first story wall line. This may be done by shifting the assembly load-drift curve from the standard set of drifts given in Table B5.1.1 to an adjusted set of drifts for each wall line, given by Equation B5.1.3.1-1. (Equation B5.1.3.1-1)

B5.1.3.2 Adjustment for openings. Each wall line load-drift curve shall account for the effects of openings within it. This may be done by applying the adjustment factor for openings, given by Equation B5.1.3.2-1 and Equation B5.1.3.2-2.

Qopen = 0.92a - 0.72a² + 0.80a³ (Equation B5.1.3.2-1)

(Equation B5.1.3.2-2)

where:

= sum of the areas of the openings within the wall line

= sum of the lengths of the full-height wall segments within the wall line.

B5.1.3.3. Adjustment for overturning. Each wall line load-drift curve shall account for the effects of overturning demand and resistance. This may be done by applying the adjustment factor for overturning, given by Equation B5.1.3.3-1 or, for existing upper-story wall lines only, by Table B5.1.3.3.

(Equation B5.1.3.3-1)

where:

Mot is the overturning demand on the wall line and Mr is the resisting moment due to all available dead loads tributary to the wall line plus the effects of any tie-down hardware.

Commentary: See FEMA P-807 Section 4.5.3.2 for guidance on calculating Qot.

B5.1.4. Story load-drift curves. For each story, in each direction, a load-drift curve shall be computed by adding the load-drift curves of all the walls in that story and aligned in that direction.

Commentary: Where all the wall line load-drift curves are mapped to the same set of drifts, the summation is straightforward. Where some first story wall lines have load-drift curves mapped to a height-adjusted set of drifts, load values at the standard drift values should be determined by linear interpolation. Once interpolated values are calculated, the various load- drift curves can again be added in a straightforward way based on the standard drift values. See FEMA P-807 Section 4.6 for additional discussion.

B5.2.1. Center of strength. The center of strength for the first and second stories shall be determined based on the wall line loads at the drift at which the story strength in the corresponding story and direction occurs.

Commentary: FEMA P-807 Section 4.6.4 illustrates the calculation of the center of strength.

B5.2.2. First story torsional demand. The first story torsional demand represents the effect of the first story strength acting at the torsional eccentricity, given by Equation B5.2.2-1.

B5.2.3. First story load-rotation curve. For the first story, a load-rotation curve shall be derived, relating torsion about the story center of strength to the resulting rotation of the story, assuming a rigid second floor diaphragm and accounting for the load-drift behavior of each first story wall line. The load-rotation curve shall consider rotation angles up to at least the rotation associated with 5 percent in-plane drift in at least one first story wall line.

Commentary: FEMA P-807 Section 4.6.6 illustrates one method for calculating of the load-rotation curve, dividing the rotation range of interest into ten even increments.

B5.3.1. Base-normalized upper-story strength. The base-normalized upper-story strength shall be calculated for each principal direction per Equation B5.3.1-1.

(Equation B5.3.1-1)

B5.3.2. Weak-story ratio. The weak-story ratio shall be calculated for each principal direction per Equation B5.3.2-1. (Equation B5.3.2-1)

B5.3.3. Strength degradation ratio. The strength degradation ratio, CD , shall be calculated for each principal direction based on the first story load-drift curves.

Commentary: FEMA P-807 Section 4.7.4 illustrates the calculation of the strength degradation ratio.

B5.3.4. Torsion coefficient. The torsion coefficient, given by Equation B5.3.4-1, need not be taken greater than 1.4. (Equation B5.3.4-1)

B5.3.5. Story height factor. The story height factor shall be calculated for each principal direction per Equation B5.3.5-1, where H1 is given in inches.

Qs = 0.55 + 0.0047 H1 (Equation B5.3.5-1)

B6.1. Evaluation relative to the performance objective. Subject to the additional requirements of Bulletin Section B1.2, any eligible structure shall be deemed to comply with the requirements of this Bulletin if its spectral capacity in each principal direction exceeds the spectral demand.

B6.1.1. Spectral capacity. Spectral capacity in each direction shall be calculated from Equations B6.1.1-1 through

B6.1.1-5, using drift limit POE adjustment factors given in Table B6.1.1 for the drift limit POE specified in Bulletin

Section B1.1.3. Drift limit POE adjustment factors for intermediate values of drift limit POE shall be calculated by linear interpolation.

Commentary: SFEBC Chapter 5E does not require the calculation of a POE. However, given a spectral demand, the POE of a structure can be calculated. See FEMA P-807 Section 5.4.2 or Appendix B model provision 6.2.

(Equation B6.1.1-1)

(Equation B6.1.1-2)

(Equation B6.1.1-3)

(Equation B6.1.1-4)

(Equation B6.1.1-5)

Table B6.1.1. Drift limit probability of exceedance adjustment factors.

B7.1. Retrofitted first story strength. The first story strength of the retrofitted structure shall account for all existing unaltered elements, existing altered elements, new elements provided to increase story strength, and new elements provided to correct aspects of eligibility or building survey non-compliance.

Exception: Out-of-plane or weak axis strength of existing or retrofit elements need not be considered where the sum of those strengths is deemed insignificant to the total story strength.

Commentary: The Exception is intended to allow wood frame walls and pin-based frames to be ignored in their weak directions, and to allow the Department to accept the engineer’s judgment or to require modeling of fixed-based frames and cantilever columns in their weak directions.

B7.2. Retrofit compliance. The retrofit design shall demonstrate that both of the following conditions are true:

1. The retrofitted structure’s spectral capacity in each principal direction exceeds the spectral demand.

2. The first story strength of the retrofitted structure in each principal direction satisfies Equation B7.2-1. (Equation B7.2-1)

Commentary: The intent of Equation B7.2-1 is to ensure that over-strengthening the first story is not miscounted as beneficial. Given the maximum POE, if the required first story strength cannot be achieved without exceeding this limit, it indicates that the proposed retrofit would push failure to the second story and would not achieve its intended effect. Where the exception to Bulletin Section

B1.1.3 is applied, the higher POE value will give the same spectral capacity for less first story strength, effectively allowing a lighter retrofit that might satisfy the equation.

FEMA P-807 Section 6.2.1 provides formulas for estimating the strength of the retrofitted first story needed to reach the required spectral capacity, but use of the estimating formulas is not required.

demonstrate that all of the following additional conditions is true:

1. The first story strength of the retrofitted structure in each principal direction satisfies Equation B7.3-1.

2. The retrofit design satisfies the requirements of Bulletin Section B7.3.1.

(Equation B7.3-1)

B7.3.1 Minimized torsional eccentricity. Retrofit elements shall be located along perimeter wall lines so as to minimize the torsional eccentricity of the retrofitted structure, or so as to satisfy Equations B7.3.1-1 and B7.3.1-2.

This requirement may be waived with the approval of the Department to accommodate other building or planning code requirements or to avoid disproportionate construction costs.

(Equation B7.3.1-2)

B7.4 Design criteria for retrofit elements. Retrofit elements shall conform to the general requirements in this section and to the applicable requirements in the following subsections.

Commentary: See Bulletin Section B3.4 for discussion of retrofit systems for which FEMA P-807 is suitable.

1. Where retrofit elements are sized based on unit strengths from codes or standards, the expected strength, without strength reductions or resistance factors, may be used.

Commentary: The allowance of expected strength, which is typically greater than nominal strength (see Bulletin Section A3.2.2) is appropriate because FEMA P-807 requires retrofit elements to be ductile (or, in ASCE 31 or ASCE 41 terms, deformation-controlled).

2. The load-drift curve of each retrofit element type shall be based on expected material properties, including overstrength. The full expected capacity, without strength reduction or resistance factors, shall be used to calculate load-drift curves and peak strengths.

3. Each retrofit element shall be such that a load-drift curve based on similar elements alone would have a strength degradation ratio, CD , greater than or equal to 0.8.

4. The load-drift curve of each retrofit element type shall be defined up to five percent interstory drift or as needed to fully characterize the retrofit design per Bulletin Section B5.

5. Materials and systems for all retrofit elements shall be generally consistent with provisions of the building code for new construction of the same occupancy and risk category. SFEBC Section 302.4 and other provisions that allow like materials for alterations do not apply to retrofits mandated by SFEBC Chapter 5E. However, the Department may waive restrictions on certain systems based on building height, irregularity, seismic design category, or other conditions not related to the critical deficiencies of the story being evaluated or retrofitted.

Commentary: FEMA P-807 presumes that retrofit elements will be reliably ductile (as indicated by the requirement for a minimum CD value in item 3 above). Systems detailed as special should generally be deemed to comply with this requirement, but systems detailed as intermediate or ordinary may also be shown to be adequate. The final sentence of this provision allows intermediate and ordinary steel frames to be used in seismic design category D and E; see also ASCE 7-16 Sections 12.2.5.6 and 12.2.5.7.

6. Design criteria for load path components and connections shall be appropriate to the performance objective and shall be based on the building code for new construction, appropriate provisions of other criteria allowed by SFEBC Section 506E.2, or principles of capacity design.

B7.4.1. Wood structural panel shear walls. Load-drift curves for wood structural panel retrofit elements shall be calculated in accordance with Bulletin Section B5. Existing shear walls modified by replacing sheathing materials or by adding supplemental wood structural panels shall be considered retrofit elements.

B7.4.2. Steel special moment-resisting frames. Steel retrofit elements that conform to the requirements of AISC 34105 or AISC 341-10 for Special Moment Frames shall be deemed to comply with the provision requiring a CD value greater than or equal to 0.8. The load-drift curve may be characterized per FEMA P-807 Figure 6-7 as follows: Vy = ZFye with post-yield strengthening up to 1.2Vy at dmax , with dmax = dy + 4% .

B7.4.3. Steel intermediate moment-resisting frames. For steel retrofit elements that conform to the requirements of AISC 341 for Intermediate Moment Frames, the load-drift curve may be characterized per FEMA P-807 Figure 6-7 as follows: Vy = ZFye with no post-yield strengthening, and dmax = dy + 2% .

B7.4.4. Steel ordinary moment-resisting frames. For steel retrofit elements that conform to the requirements of AISC 341 for Ordinary Moment Frames, the load-drift curve may be characterized per FEMA P-807 Figure 6-7 as follows: Vy per AISC 360 Chapter F, using Fye instead of Fy , dmax = 2% .

B7.4.5. Steel special cantilever columns. For steel retrofit elements that conform to the requirements of AISC 341 for Special Cantilevered Column systems, the load-drift curve may be characterized per FEMA P-807 Figure 6-7 as follows: Vy = ZFye with no post-yield strengthening, and dmax = dy + 2% .

B7.4.6. Steel ordinary cantilever columns. FEMA P-807 shall not be used to demonstrate compliance of steel ordinary cantilever columns as retrofit elements.

B7.4.7. Steel buckling-restrained braced frames. Steel retrofit elements that conform to the requirements of AISC 341 for buckling-restrained braced frames shall be deemed to comply with the provision requiring a CD value greater than or equal to 0.8.

Commentary: FEMA P-807 Section 6.5.5 offers further guidance on characterizing and designing these elements.

B7.4.8. Damping systems. FEMA P-807 may be used to demonstrate compliance of hysteretic damping systems that rely on the yielding of steel components by modeling the retrofit elements as bi-linear systems similar to other structural steel systems. The Department is authorized to require third party peer review at the expense of the permit applicant.

FEMA P-807 shall not be used to demonstrate compliance of other damping systems, including viscous- or frictiondamped systems.

Commentary: Viscous- and friction-damped systems cannot be designed with FEMA P-807 because the FEMA P-807 surrogate models did not include these mechanisms.

B7.5 Design criteria for load path elements and components. The retrofit design shall confirm or provide a load path from the second floor diaphragm through the first story seismic force-resisting elements and their foundations, to the supporting soils. The ultimate strength of load path components shall be reduced with strength reduction factors as needed to ensure that the load-path elements are able to develop the strength and the intended mechanism of first story wall and frame elements. Specific design criteria may be derived from principles of capacity design, from other

criteria allowed by SFEBC Section 506E.2, or from building code provisions for new construction involving the overstrength factor, Ω 0 .

B7.5.1. Foundations and overturning. New foundation elements shall be provided as needed to resist bearing, sliding, and overturning forces associated with the retrofit elements acting at their strength. Connections and load path components related to wall or frame overturning shall not assume any acting dead load except for the self-weight of the retrofit element unless the retrofit element incorporates existing gravity load-carrying framing or unless the design and construction explicitly transfer existing dead load to the retrofit element. The weight of foundation elements may be considered if adequately connected.

B7.5.2. Second floor diaphragm. The second floor diaphragm shall be strengthened as needed to ensure that expected forces can be transferred between the diaphragm and the first-story elements.

B7.5.3. Fixed-base frame columns. Moment-resisting frame systems and cantilever column systems whose capacity assumes other than a pin-based condition shall be provided with connection details demonstrated to develop the assumed fixity and the assumed column strength. In general, an anchor-bolted base plate without substantial embedment within a foundation element is not considered to provide a fixed-base condition.

B8.1. Structural calculations. Structural calculations and documentation of evaluations and retrofit designs using FEMA P-807 shall include, at minimum:

1. Plans and/or elevations for each floor level identifying each wall line and showing the wall assembly, length, location, and openings.

2. A schedule of wall assemblies and load drift curves for existing, altered, and new elements.

3. A list or schedule of wall lines with overturning and opening adjustments.

4. Derivation of characteristic coefficients.

5. Spectral capacity calculations.

6. Site-specific spectral demand calculations.