Bell Municipal Code Ch. 15.32 Earthquake Hazard Protection for Existing Buildings

A. The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury to persons and damage to property that may result from the effect of earthquake damage on buildings which have unreinforced masonry bearing walls. Such buildings have been widely recognized for their susceptibility to structural earthquake damage.

B. This chapter shall not be deemed to require electrical, plumbing, mechanical or fire safety systems existing in buildings which are of unreinforced masonry construction to be altered when work is required to be accomplished as to such buildings, unless such systems constitute a hazard to life or property.

C. This chapter provides systematic procedures and standards for identification and classification of buildings which have unreinforced masonry bearing walls, based on their present use. Priorities, time periods and standards are also established under which these buildings are required to be structurally analyzed and anchored. Where the analysis determines the existence of structural deficiencies, this chapter requires the building to be strengthened or demolished.

D. This chapter also provides a method by which the city may, on an emergency basis, order the repair and/or rehabilitation of buildings and structures suffering structural damage in an earthquake.

E. Portions of the State Historical Building Code ("SHBC") established under Part 8, Title 24 of the California Code of Regulations are included in this chapter.

(Prior code § 6475)

A. The provisions of this chapter shall apply to all buildings in existence as of the effective date of the ordinance codified in this chapter which have unreinforced masonry bearing walls as defined in this chapter.

B. Exception. This chapter shall not apply to detached one- or two-family dwellings and detached apartment houses containing fewer than five dwelling units and used solely for residential purposes.

(Prior code § 6476)

In addition to the definitions set forth in the city's zoning regulations and building regulations, the following definitions shall apply to this chapter:

"Building"

means any building or structure which has one or more unreinforced masonry bearing wall.

"Director"

means the director of community development of the city.

"Essential building"

means any building housing a hospital or other medical facility having surgery or emergency treatment areas, fire or police stations, municipal government disaster operation and communication centers.

"High-risk building"

means any building not classified an essential building having an occupant load as determined pursuant to this title of 100 occupants or more.

Exception: A high-risk building shall not include the following:

Any building having exterior walls braced with masonry cross walls or woodframe cross walls spaced less than 40 feet apart in each story. Cross walls shall be full-story height with a minimum length of one and one-half times the story height;

Any building used for its intended purpose, as determined by the director, for less than 20 hours per week.

"Historical building"

means any building designated as a historical building by an appropriate federal, state or city jurisdiction.

"Low-risk building"

means any building not classified as an essential building having an occupant load as determined by Section 91.3301(d) of less than 20 occupants.

"Medium-risk building"

means any building not classified as a high-risk building or an essential building having an occupant load as determined by this title of 20 occupants or more.

"Unreinforced masonry bearing wall"

means a masonry wall in a building having all of the following characteristics:

Provides the vertical support for a floor or roof; and

The total superimposed load is over 100 pounds per linear foot; and

The area of reinforcing steel is less than 50% of that required by this chapter.

(Prior code § 6477)

A. The rating classifications set forth in Table A, set out at the end of this chapter, are established and each building shall be placed in one such rating classification by the director. The total occupant load of the entire building as determined by this chapter shall be used to determine the rating classification.

B. Exceptions. For the purpose of this chapter, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications.

(Prior code § 6478)

A. The owner of each building shall cause a structural analysis to be made of the building by a civil or structural engineer or architect licensed by the State of California, and if the building does not meet the minimum earthquake standards specified in this chapter, the owner shall cause it to be structurally altered to conform to such standards or cause the building to be demolished.

B. The owner of a building shall comply with the requirements set forth in subsection A of this section by submitting such a structural analysis to the director for review and approval within the stated time limits:

1. Within 270 days after the service of an order referred to in Section 15.32.060, a structural analysis. Such analysis, which is subject to approval by the director, shall demonstrate that the building meets the minimum requirements of this chapter, or if such structural analysis reflects that the building does not meet the requirements of this chapter; and

2. Within 270 days after the service of such order, the owner of the building shall submit to the director for approval plans for the proposed structural alterations of the building necessary to comply to the minimum requirements of this chapter; and

3. Within 120 days after service of the order, the building owner shall submit to the director for approval plans for the installation of wall anchors in accordance with the requirements specified in this chapter; or

4. Within 270 days after the service of the order, if the building does not comply with the requirements of this chapter, and the owner has not timely commenced work to render the building in compliance with the provisions of this chapter, the owner shall demolish the building.

C. After plans are submitted and approved by the director, the owner shall obtain a building permit, and commence and complete the required construction or demolition within the time limits set forth in Table B, set out at the end of this chapter. These time limits shall begin to run from the date the order is served in accordance with subsections (B)(1) and (B)(2) of this section.

D. Owners electing to comply with subsection (B)(3) of this section are also required to comply with subsection (B)(2) or (B)(4) of this section, provided, however, that the 270 day period provided for in such subsections (B)(2) or (B)(4) and the time limits for obtaining a building permit, commencing construction and completing construction for complete structural alterations or building demolition set forth in Table B, set out at the end of this chapter, shall be extended in accordance with Table C, set out at the end of this chapter. Each such extended time limit, except the time limit for commencing construction, shall begin to run from the date the order is served in accordance with Section 15.32.060(B). The time limit for commencing construction shall commence to run from the date the building permit is issued.

(Prior code § 6479)

A. Service of Order. The director shall issue an order, as provided in Section 15.32.050(B), to the owner of each building. The director shall, upon receipt of a written request from the owner, order that a building be made to comply with this chapter prior to the times for such building set forth in this chapter.

B. Contents of Order. The order shall be in writing and shall be served either personally or by certified or registered mail upon the owner as shown on the last equalized assessment, and upon the person, if any, in apparent charge or control of the building. The order shall specify that the building has been determined by the director to be subject to the provisions of this chapter and, therefore, is required to meet the minimum seismic standards of this chapter. The order shall specify the rating classification of the building and shall be accompanied by a copy of this chapter.

C. Appeal From Order. The owner or person in charge or control of the building may appeal the director's initial determination that the building is subject to the provisions of this chapter to the city council. Such appeal shall be filed with the council within 30 days from the service date of the order. Such appeal shall be made in writing upon appropriate forms provided therefor by the director, and the grounds thereof shall be stated clearly and concisely. No appeal shall be accepted unless it is timely filed and is accompanied by a filing fee in an amount as set by council resolution.

D. Recordation.

1. At the time that the director serves an order, the director shall file with the office of the county recorder a certificate giving notice of the existence of such order. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it.

2. If the building is either demolished, found not to be within the scope of this chapter, or is structurally capable of resisting minimum seismic forces required by this chapter as a result of structural alterations or an analysis, or is repaired so that it meets the requirements of this chapter, the director shall file with the office of the county recorder a certificate stating that the order is of no further effect.

E. Enforcement. If the owner or other person in charge or control of a building fails to comply with any order issued by the director pursuant to this chapter, within any of the time limits set forth in this chapter, the director shall order that the building be vacated and that the building remain vacant until such order has been complied with. If compliance with such order has not been accomplished within a reasonable period of time, as set by the director, after the date the building has been ordered vacated or such additional time as may have been granted by the director, the director shall process a proceeding pursuant to Chapter 8.36 of this code to determine whether the building is a public nuisance, and if it is, he or she shall order its abatement.

(Prior code § 6480)

A. General. The standards and procedures established by this chapter shall apply in all aspects to a historical building except that as a means to preserve original architectural elements and facilitate restoration, a historical building may, in addition, comply with the special provisions set forth in this section.

B. Unburned Clay Masonry or Adobe. Existing or reerected walls of adobe construction shall conform to the following:

1. Unreinforced adobe masonry walls shall not exceed a height or thickness ratio of five for exterior bearing walls and must be provided with a reinforced bond beam at the top, interconnecting all walls, minimum beam depth shall be six inches and a minimum width of eight inches less than the wall width. Minimum wall thickness shall be 18 inches for exterior bearing walls and 10 inches for adobe partitions. No adobe structure shall exceed one story in height unless the historic evidence indicates a two-story height. In such cases the height-to-thickness ratio shall be the same as above for the first floor based on the total two-story height, and the second floor wall thickness shall not exceed the ratio of five by more than 20%. Bond beams shall be provided at the roof and second floor levels.

2. Foundation footings shall be reinforced concrete under newly reconstructed walls and shall be 50% wider than the wall above, soil conditions permitting, except that the foundation wall may be four inches less in width than the wall above if a rock, burned brick or stabilized adobe facing is necessary to provide authenticity.

3. New or existing unstabilized brick and adobe brick masonry shall have an average compressive strength of 225 pounds per square inch when tested in accordance with ASTM designation C67. One sample out of five may have a compressive strength of not less than 188 pounds per square inch. Unstabilized brick may be used where existing bricks are unstabilized and where the building is not susceptible to flooding conditions or direct exposure. Adobe may be allowed a maximum value of three pounds per square inch for shear with no increase for lateral forces.

4. Mortar may be of the same soil composition and stabilization as the brick in lieu of cement mortar.

5. Nominal tension stresses due to seismic forces normal to the wall may be neglected if the wall meets thickness requirements and shear values allowed by this subsection.

C. Archaic Materials. Allowable stresses for archaic materials not specified in this code shall be based on substantiating research data or engineering judgment, subject to the director's satisfaction.

D. Alternative Materials and SHBC Advisory Review. Alternative materials, design or methods of construction will be considered as allowed by this code. In addition, when a request for an alternative proposed design, material or method of construction is being considered, the director may file written request for opinion to the State Historical Building Code Advisory Board for its consideration and advice.

(Prior code § 6481)

A. General.

1. Every building shall be analyzed and constructed to resist minimum total lateral seismic forces assumed to act nonconcurrently in the direction of each of the main axes of the structure in accordance with the following equation:

V = IKCSW.....(88-1)

2. The value of IKCS need not exceed the values set forth in Table D, set out at the end of this chapter, based on the applicable rating classification of the building.

B. Lateral Forces on Elements of Structures.

1. Parts or portions of structures shall be analyzed and designed for lateral loads in accordance with the provisions of this section of this code but not less than the value from the following equation:

Fp = ICp SWp.....(88-2)

2. For the provisions of this subsection, the product of IS need not exceed the values as set forth in Table E, set out at the end of this chapter. Exception: Unreinforced masonry walls in buildings not having a rating classification of I may be analyzed in accordance with Section 15.32.090.

3. The value of Cp need not exceed the values set forth in Table F, set out at the end of this chapter.

C. Anchorage and Interconnection. Anchorage and interconnection of all parts, portions and elements of the structure shall be analyzed and designed for lateral forces in accordance with Table F of this code, set out at the end of this chapter, and the equation Fp = ICp SWp as modified by Table E, set out at the end of this chapter. Minimum anchorage of masonry walls to each floor or roof shall resist a minimum force of 200 pounds per linear foot acting normal to the wall at the level of the floor or roof.

D. Level of Required Repair. Alterations and repairs required to meet the provisions of this chapter shall comply with all other applicable requirements of this code unless specifically provided for in this chapter.

E. Required Analysis.

1. General. Except as modified herein, the analysis and design relating to the structural alteration of a building shall be in accordance with the analysis specified in this chapter.

2. Continuous Stress Path. A complete, continuous stress path from every part or portion of the building to the ground shall be provided for the required horizontal forces.

3. Positive Connections. All parts, portions or elements of the building shall be interconnected by positive means.

F. Analysis Procedure.

1. General. Stresses in materials and existing construction utilized to transfer seismic forces from the ground to parts or portions of the structure shall conform to those permitted by the code and those materials and types of construction specified in this chapter.

2. Connections. Materials and connectors used for interconnection of parts and portions of the structure shall conform to the code. Nails may be used as part of an approved connector.

3. Unreinforced Masonry Walls.

a. Except as modified herein, unreinforced masonry walls shall be analyzed as specified in this code and to withstand all vertical loads as specified in this code in addition to the seismic forces required by this chapter. The 50% increase in the seismic force factor for shear walls as specified in this code may be omitted in the computation of seismic loads to existing shear walls.

b. No allowable tension stress will be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this chapter shall be strengthened or shall be removed and replaced. Exception: (1) Unreinforced masonry walls in buildings not classified as a Rating Classification I pursuant to Table A, set out at the end of this chapter, may be analyzed in accordance with this section; (2) Unreinforced masonry walls which carry no design loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements.

G. Combination of Vertical and Seismic Forces.

1. New Materials. All new materials introduced into the structure to meet the requirements of this chapter which are subjected to combined vertical and horizontal forces shall comply with the provisions of this title.

2. Existing Materials. When stresses in existing lateral force-resisting elements are due to a combination of dead loads plus seismic loads, the allowable working stress specified in the code may be increased 100%. However, no increase will be permitted in the stresses allowed in this chapter and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by this title.

3. Allowable Reduction of Bending Stress by Vertical Lead. In calculating tensile fiber stress due to seismic forces required by this chapter, the maximum tensile fiber stress may be reduced by the full direct stress due to vertical dead loads.

(Prior code § 6482)

A. General. All materials permitted by this code, including their appropriate allowable stresses and those existing configurations of materials specified herein, may be utilized to meet the requirements of this chapter.

B. Existing Materials.

1. Unreinforced Masonry Walls.

a. Unreinforced masonry walls analyzed in accordance with this section may provide vertical support for roof and floor construction and resistance to lateral loads. The bonding of such walls shall be as specified in this title.

b. Tension stresses due to seismic forces normal to the wall may be neglected if the wall does not exceed the height or length-to-thickness ratio and the in-plane shear stresses due to seismic loads as set forth in Table G, set out at the end of this chapter.

c. If the wall height-thickness ratio exceeds the specified limits, the wall may be supported by vertical bracing members designed in accordance with this chapter. The deflection of such bracing member at design loads shall not exceed one-tenth of the wall thickness. Exception: The wall may be supported by flexible vertical bracing members designated in accordance with Section 15.32.080(B) if the deflection at design loads is not less than one quarter nor more than one-third of the wall thickness.

d. All vertical bracing members shall be attached to floor and roof construction for their design loads independently of required wall anchors. Horizontal spacing of vertical bracing members shall not exceed one-half the unsupported height of the wall nor 10 feet.

e. The wall height may be measured vertically to bracing elements other than a floor or roof. Spacing of the bracing elements and wall anchors shall not exceed six feet. Bracing elements shall be detailed to minimize the horizontal displacement of the wall by components of vertical displacements of the floor or roof.

2. Existing Roof, Floors, Walls, Footings and Wood Framing. Existing materials, including wood shear walls utilized in the described configuration, may be used as part of the lateral load-resisting system, provided that the stresses in the materials do not exceed the values shown in Table No. 88-H.

C. Strengthening of Existing Materials. New materials, including wood shear walls, may be utilized to strengthen portions of the existing seismic resisting system in the described configurations, provided that the stresses do not exceed the values shown in Table I, set out at the end of this chapter.

D. Alternate Materials. Alternate materials, designs and methods of construction may be approved by the director.

E. Minimum Acceptable Quality of Existing Unreinforced Masonry Walls.

1. General Provisions. All unreinforced masonry walls utilized to carry vertical loads and seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this subsection. All masonry quality shall equal or exceed the minimum standards established herein or shall be removed and replaced by new materials. Alternate methods of testing may be approved by the director. The quality of mortar in all masonry walls shall be determined by performing in-place shear tests or by testing eight-inch diameter cores. Alternative methods of testing may be approved by the department. Nothing shall prevent pointing with mortar of all the masonry wall joints before the tests are first made. Prior to any pointing, the mortar joints must be raked and cleaned to remove loose and deteriorated mortar. Mortar for pointing shall be Type S or N except masonry cements shall not be used. All preparation and mortar pointing shall be done under the continuous inspection of a registered deputy building inspector. At the conclusion of the inspection, the inspector shall submit a written report to the licensed engineer or architect responsible for the seismic analysis of the building setting forth the result of the work inspected. Such report shall be submitted to the director for approval as part of the structural analysis. All testing shall be performed in accordance with the requirements specified in this subsection by a testing agency approved by the director. An accurate record of all such tests and their location in the building shall be recorded and these results shall be submitted to the director for approval as part of the structural analysis.

2. Number and Location of Tests. The minimum number of tests shall be two per wall or line of wall elements resisting a common force, or one per 1,500 square feet of wall surface, with a minimum of eight tests in any case. The exact test or core location shall be determined at the building site by the licensed engineer or architect responsible for the seismic analysis of the subject building.

3. In-Place Shear Tests. The bed joints of the outer wythe of the masonry shall be tested in shear by laterally displacing a single brick relative to the adjacent bricks in that wythe. The opposite head joint of the brick to be tested shall be removed and cleaned prior to testing. The minimum quality mortar in 80% of the shear tests shall not be less than the total of 30 psi plus the axial stress in the wall at the point of the test. The shear stress shall be based on the gross area of both bed joints and shall be that at which movement of the brick is first observed.

4. Core Tests. A minimum number of mortar test specimens equal to the number of required cores shall be prepared from the cores and tested as specified herein. The mortar joint of the outer wythe of the masonry core shall be tested in shear by placing the circular core section in a compression testing machine with the mortar bed joint rotated 15 degrees from the axis of the applied load. The mortar joint tested in shear shall have an average ultimate stress of 20 psi based on the gross area. The average shall be obtained from the total number of cores made. If test specimens cannot be made from cores taken then the shear value shall be reported as zero.

F. Testing of Shear Bolts.

1. One-fourth of all new shear bolts and dowels embedded in unreinforced masonry walls shall be tested by a registered deputy building inspector using a torque calibrated wrench to the following minimum torques:

1/2-inch-diameter bolts or dowels—40 foot-lbs.

5/8-inch diameter bolts or dowels—50 foot-lbs.

3/4-inch diameter bolts or dowels—60 foot-lbs.

2. No bolts exceeding three-quarter inch shall be used. All nuts shall be installed over malleable iron or plate washers when bearing on wood and heavy cut washers when bearing on steel.

G. Determination of Allowable Stresses for Design Methods Based on Test Results.

1. Design Shear Values.

a. Design seismic in-plane shear stresses shall be substantiated by tests performed as specified in subsections (E)(3) and (E)(4) of this section.

b. Design stresses shall be related to test results obtained in accordance with Table J, set out at the end of this chapter. Intermediate values between three and ten (10) psi may be interpolated.

2. Design Compression and Tension Values. Compression stresses for unreinforced masonry having a minimum design shear value of three psi shall not exceed 100 psi. Design tension values for unreinforced masonry shall not be permitted.

H. Five percent of the existing rod anchors utilized as all or part of the required wall anchors shall be tested in pullout by an approved testing laboratory. The minimum number tested shall be four per floor, with two tests at walls with joists framing into the wall and two tests at walls with joists parallel to the wall. The test apparatus shall be supported on the masonry wall at a minimum distance of the wall thickness from the anchor tested. The rod anchor shall be given a preload of 300 pounds prior to establishing a datum for recording elongation. The tension test load reported shall be recorded at one-eighth inch relative movement of the anchor and the adjacent masonry surface. Results of all tests shall be reported. The report shall include the test results as related to the wall thickness and joist orientation. The allowable resistance value of the existing anchors shall be 40% of the average of those tested anchors having the same wall thickness and joist orientation.

I. Qualification tests for devices used for wall anchorage shall be tested with the entire tension load carried on the enlarged head at the exterior face of the wall. Bond on the part of the device between the enlarged head and the interior wall face shall be eliminated for the qualification tests. The resistance value assigned the device shall be 20% of the average of the ultimate loads.

(Prior code § 6483)

A. General. In addition to the seismic analysis required elsewhere by this chapter, the licensed engineer or architect responsible for the seismic analysis of the building shall determine and record the information required by this section on the approved plans.

B. Construction Details. The following requirements with appropriate construction details shall be made part of the approved plans:

a. All unreinforced masonry walls shall be anchored at the roof level by tension bolts through the wall as specified in Table I, set out at the end of this chapter, or by approved equivalent at a maximum anchor spacing of six feet. Anchors installed in accordance with this title shall be accepted as conforming to this requirement.

b. All unreinforced masonry walls shall be anchored at all floors with tension bolts through the wall or by existing rod anchors at a maximum anchor spacing of six feet. All existing rod anchors shall be secured to the joists to develop the required forces. The director may require testing to verify the adequacy of the embedded ends of existing rod anchors. Tests when required shall conform to Section 15.32.090.

c. When access to the exterior face of the masonry wall is prevented by proximity of an existing building, wall anchors conforming to Items 5 and 6 in Table I, set out at the end of this chapter, may be used.

d. Alternative devices to be used in lieu of tension bolts for masonry wall anchorage shall be tested as specified in Section 15.32.090.

2. Diaphragm chord stresses of horizontal diaphragms shall be developed in existing materials or by addition of new materials.

3. Where trusses and beams other than rafters or joists are supported on masonry, ledges or columns shall be installed to support vertical loads of the roof or floor members.

4. Parapets and exterior wall appendages not capable of resisting the forces specified in this chapter shall be removed, stabilized or braced to ensure that the parapets and appendages remain in their original position.

5. All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N mortar. Prior to any pointing, the wall surface must be raked and cleaned to remove loose and deteriorated mortar. All preparation and pointing shall be done under the continuous inspection of a registered deputy building inspector certified to inspect masonry or concrete. At the conclusion of the project, the inspector shall submit a written report to the director setting forth the portion of work inspected.

6. Repair details of any cracked or damaged unreinforced masonry wall required to resist forces specified in this chapter.

C. Existing Construction. The following existing construction information shall be made part of the approved plans:

1. The type and dimensions of existing walls and the size and spacing of floor and roof members;

2. The extent and type of existing wall anchorage to floors and roof;

3. The extent and type of parapet corrections which were performed in accordance with this code;

4. Accurately dimensioned floor plans and masonry wall elevations showing dimensioned openings, piers, wall thickness and heights;

5. The location of cracks or damaged portions of unreinforced masonry walls requiring repairs;

6. The type of interior wall surfaces and if reinstalling or anchoring of ceiling plaster is necessary;

7. The general condition of the mortar joints and if the joints need pointing.

(Prior code § 6484)

Whenever an order of abatement is issued pursuant to Chapter 8.36 of this code, which order requires reconstruction or repair of a building, the provisions of Section 15.32.070 et seq., of this chapter shall apply to all work of reconstruction and repair required pursuant to such order.

(Prior code § 6486)

Tables A through J, set out following this chapter, are made a part of this code by this reference, and shall apply as provided in this chapter.

Table A RATING CLASSIFICATIONS

Table B TIME LIMITS FOR COMPLIANCE

Times set forth in this table shall run from the date an order is issued pursuant to this chapter.

Table C SERVICE PRIORITIES AND EXTENDED TIME PERIODS

Table D HORIZONTAL FORCE FACTORS BASED ON RATING CLASSIFICATION

Table E HORIZONTAL FORCE FACTORS "IS" FOR PARTS OR PORTIONS OF STRUCTURES

Table F HORIZONTAL FORCE FACTOR "C" FOR PARTS OR PORTIONS OF BUILDINGS OR OTHER STRUCTURES

Notes:

Table G ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS WITH MINIMUM QUALITY MORTAR 1, 2

Table H VALUES FOR EXISTING MATERIALS

Table I ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION

Table J ALLOWABLE SHEAR STRESS FOR TESTED UNREINFORCED MASONRY WALLS

(Prior code § 6485)