Azusa Municipal Code Art. XIII Earthquake Hazard Reduction in Existing Buildings

(a) The purpose of this article is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on unreinforced masonry bearing wall buildings constructed before 1934. Such buildings have been widely recognized for sustaining life hazardous damage as a result of partial or complete collapse during moderate to strong earthquakes. This is particularly important in the city where many buildings are of the pre-1934 type.

(b) The provisions of this article are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury and will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. This article shall not require existing electrical, plumbing, mechanical or fire safety systems to be altered unless they constitute a hazard to life or property.

(c) This article provides systematic procedures and standards for identification and classification of unreinforced masonry bearing wall buildings based on their 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 deficiencies, this article requires the building to be strengthened or demolished.

(d) The provisions of the State Historical Building Code (SHBC) established under part 8, title 24 of the State Administrative Code are incorporated in this article.

(Code 1971, § 15.10.010)

This article shall apply to all buildings constructed or under construction prior to October 6, 1933, or for which a building permit was issued prior to October 6, 1933, which as of October 3, 1985, have reinforced masonry bearing walls. This article shall not apply to detached one- or two-family dwellings and detached apartment houses containing less than five dwelling units and used solely for residential purposes.

(Code 1971, § 15.10.020)

For purposes of this article, the applicable definitions in sections 2302 and 2312 of the county's building code shall apply, and the following words, terms and phrases, when used in this article, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning:

Building Code means the County of Los Angeles Building Code, 1992 edition.

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

High-risk building means any building not classified as an essential building, having an occupant load as determined by building code section 3302 of 100 occupants or more. However, a high-risk building shall not include the following:

(1) Any building having exterior walls braced with masonry crosswalls or wood frame crosswalls spaced less than 40 feet apart in each story. Crosswalls shall be full story height with a minimum length of 1½ times the story height.

(2) Any building used for its intended purpose, as determined by the building official, for less than 20 hours per week.

Historical building means any building designated as an 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 building code section 3302 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 building code section 3302 of 20 occupants or more.

Unreinforced masonry bearing wall means a masonry wall having all of the following characteristics:

(1) Provides the vertical support for a floor or roof.

(2) The total superimposed load is over 100 pounds per linear foot.

(3) The area of reinforcing steel is less than 50 percent of that required by building code section 2417(j)3.

(Code 1971, § 15.10.030)

Cross reference— Definitions and rules of construction generally, § 1-2.

The rating classifications as exhibited in the table no. A in section 14-391 are established and each building within the scope of this article shall be placed in one such rating classification by the building official. The total occupant load of the entire building as determined by building code section 3302 shall be used to determine the rating classification. However, for the purpose of this article, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications.

(Code 1971, § 15.10.040)

(a) Service. The building official shall issue an order, as provided in subsection (b) of this section, to the owner of each building within the scope of this article in accordance with the minimum time periods for service of such orders set forth in table no. C. The minimum time period for the service of such orders shall be measured from the effective date of the ordinance from which this article is derived. The building official shall, upon receipt of a written request from the owner, order a building to comply with this article prior to the normal service date for such building set forth in this section.

(b) Contents. The order shall be in writing and shall be served either personally or by certified or registered mail upon the owner 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 building official to be within the scope of this article and, therefore, is required to meet the minimum seismic standards of this article. The order shall specify the rating classification of the building and shall be accompanied by a copy of this article which sets forth the owner's alternatives and time limits for compliance.

(c) Appeal. The owner or person in charge or control of the building may appeal the building official's initial determination that the building is within the scope of this article to the city manager. Such appeal shall be filed with the building official within 30 days from the service date of the order described in subsection (b) of this section. Any such appeal shall be decided by the city manager not later than 60 days after the date that the appeal is filed. Such appeal shall be made in writing upon appropriate forms provided therefor by the building official, and the grounds thereof shall be stated clearly and concisely. Each appeal to the city manager shall be accompanied by a filing fee as set by resolution of the city council. Within ten days after issuance of the decision of the city manager, the owner or person in charge or control may appeal that decision to the city council. Such appeal shall be made in writing upon appropriate forms provided therefor by the city clerk and the grounds thereof shall be stated clearly and concisely. Each appeal to the city council shall be filed with the city clerk and shall be accompanied by a filing fee as set by resolution of the city council.

(d) Recordation. At the time the building official serves such order, the building official shall file with the office of the county recorder a certificate stating that such building is within the scope of this article. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it where compliance with this article is not exhibited.

(e) Termination of status. If the building is either demolished, found not to be within the scope of this article or is structurally capable of resisting minimum seismic forces required by this article as a result of structural alterations or an analysis, the building official shall file with the office of the county recorder a certificate terminating the status of such building as being classified within the scope of this article.

(f) Enforcement. If the owner or other person in charge or control of the building fails to comply with any order issued by the building official pursuant to this article within any of the time limits set forth in section 14-386, the building official shall order that the entire building be vacated and that the building remain vacated until such order has been complied with. If compliance with such order has not been accomplished within 90 days after the date the building has been ordered vacated or such additional time as may have been granted by the community development director, the building official may order its demolition in accordance with the provisions of article XIV of this chapter.

(Code 1971, § 15.10.050; Ord. No. 98-09, § 2, 6-15-98)

(a) The owner of each building within the scope of this article shall cause a structural analysis to be made of the building by a civil or structural engineer or architect licensed by the state, and, if the building does not meet the minimum earthquake standards specified in this article, 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 within the scope of this article shall comply with this article by submitting the following to the building official for review within the stated time limits:

(1) Within 270 days after the service of the order described in section 14-385, a structural analysis; such analysis, which is subject to approval of the building official, shall demonstrate that the building meets the minimum requirements of this article;

(2) Within 270 days after the service of such order, the structural analysis and plans for the proposed structural alterations of the building necessary to comply to the minimum requirements of this article;

(3) Within 120 days after service of such order, plans for the installation of wall anchors in accordance with the requirements specified in section 14-388; or

(4) Within 270 days after the service of the order, plans for the demolition of the building.

(c) After the plans are submitted and approved by the building official, the owner shall obtain a building permit, commence and complete the required construction or demolition within the time limits set forth in table no. B in section 14-391. These time limits shall begin to run from the date the order is served in accordance with section 14-385(a) and (b).

(d) Owners electing to comply with subsection (b)(3) of this section are also required to comply with subsection (b)(2) or (4) of this section; provided, however, that the 270-day period provided for in subsections (b)(2) and (4) of this section 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 no. B in section 14-391 shall be extended in accordance with table no. C in section 14-391. 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 14-385(b). The time limit for commencing construction shall commence to run from the date the building permit is issued.

(Code 1971, § 15.10.060)

(a) Generally. The standards and procedures established by this article shall apply in all respects to a historical building (as defined in the state historic building code), 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 length to 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 ten 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 provided in this subsection for the first floor based on the total two-story height, and the second floor wall thickness shall not exceed the ratio five by more than 20 percent. 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 percent wider than the wall as provided in subsection (b)(1) of this section, soil conditions permitting, except that the foundation wall may be four inches less in width than such wall if a rockburned brick or stabilized adobe facing is necessary to provide authenticity.

(3) 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 185 pounds per square inch. Unstabilized brick may be used 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 the building code shall be based on substantiating research data or engineering judgment subject to the building official's satisfaction.

(d) Alternative materials and SHBC advisory review. Alternative materials, design or methods of construction will be considered as set forth in section 14-389. In addition, when a request for an alternative proposed design, material or method of construction is being considered, the building official may file a written request for opinion to the state historical building code advisory board for its consideration, advice or findings in accordance with SHBC.

(Code 1971, § 15.10.070)

(a) Generally. Every structure within the scope of this article shall be analyzed and constructed to resist minimum total lateral seismic forces assumed to act nonconcurrently in the direction of each main axis of the structure in accordance with the following equation:

V = IKCSW FORMULA (8-1)

The value of IKCSW need not exceed the values set forth in table no. D in section 14-391 based on the applicable rating classification of the building.

(b) Lateral forces on elements of structures. Parts or portions of structures shall be analyzed and designed for lateral loads in accordance with subsection (a) of this section and building code section 3212(d), but not less than the value from the following equation:

F p -IC p SW p FORMULA (8-2)

For the provisions of this subsection, the product of IS need not exceed the values as set forth in table no. E in section 14-391.

Exception: Unreinforced masonry walls in buildings not having a rating classification of I may be analyzed in accordance with section 14-389.

(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 the equation F p -IC p SW p (8-2) as modified by table no. E in section 14-391. 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 article shall comply with all other applicable requirements of the building code unless specifically provided for in this article.

(e) Required analysis.

(1) Generally. Except as modified in this section, the analysis and design relating to the structural alteration of existing structures within the scope of this article shall be in accordance with the analysis specified in building code chapter 23.

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

(3) Positive connections. All parts, portions or elements of the structure shall be interconnected by positive means.

(f) Analysis procedure.

(1) Generally. 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 building code, and those materials and types of construction specified in section 14-389.

(2) Connections. Materials and connectors used for interconnection of parts and portions of the structure shall conform to the building code.

(3) Unreinforced masonry walls. Except as modified in this section, unreinforced masonry walls shall be analyzed as specified in sections 2407, 2409 and 2419 of the building code to withstand all vertical loads as specified in chapter 23 of the building code, in addition to the seismic forces required by this article. The 50-percent increase in the seismic force factor for shear walls as specified in table no. 24-H of the building code may be omitted in the computation of seismic loads to existing shear walls. No allowable tension stress will be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this article shall be strengthened or shall be removed and replaced.

Exceptions:

a. Unreinforced masonry walls in buildings not classified as a rating classification I pursuant to table no. A in section 14-391 may be analyzed in accordance with section 14-389.

b. An unreinforced masonry wall which carries no design loads other than its own weight may be considered as veneer if it is 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 section which are subjected to combined vertical and horizontal forces shall comply with section 2312(j)2 of the building code.

(2) Existing materials. When stress in existing lateral force resisting elements are due to a combination of dead loads plus live loads plus seismic loads, the allowable working stress specified in the building code may be increased 100 percent. However, no increase will be permitted in the stresses allowed in section 14-389, and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by section 2303(d) of the building code.

(Code 1971, § 15.10.080)

(a) Generally. All materials permitted by the building code, including their appropriate allowable stresses and those existing configurations of materials specified in this section, may be utilized to meet the requirements of this article.

(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 specified in section 2412(b)1 of the building code.

b. Tension stresses due to seismic forces normal to the wall may be neglected if the wall does not exceed the height-to-thickness or length-to-thickness ratio and the in-place shear stresses due to seismic loads as set forth in tables no. F and I in section 14-391.

c. If the wall height-to-thickness ratio exceeds the specified limits, the wall may be supported by vertical bracing members designed in accordance with section 14-388(f). 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 designed in accordance with section 14-388(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 ten 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 these materials do not exceed the values shown in table no. G in section 14-391.

(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 no. H in section 14-391.

(d) Alternate materials. Alternate materials, designs and methods of construction may be approved by the building official in accordance with the provisions of section 105 of the building code.

(e) Minimum acceptable quality of existing unreinforced masonry walls.

(1) Generally. 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 in this article or shall be removed and replaced by new materials. 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 building official. 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 building official 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 building official. An accurate record of all such tests and their location in the building shall be recorded, and these results shall be submitted to the building official 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 hundred 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 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 percent 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 the 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 in this section. 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 loan. The mortar joint tested in shear shall have an average ultimate stress based on 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, the shear value shall be reported as zero.

(f) Testing of shear bolts. 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:

½-inch diameter bolts or dowels = 40 foot-lbs

⅝-inch diameter bolts or dowels = 50 foot-lbs

¾-inch diameter bolts or dowels = 60 foot-lbs

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

(g) Determination of allowable stresses for design methods based on test results.

(1) Design shear values. Design seismic in-place shear stresses shall be substantiated by tests performed as specified in subsections (e)(3) and (4) of this section. Design stresses shall be related to test results obtained in accordance with table no. I in section 14-391. Intermediate values between three and ten 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) Rod anchors. 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 percent of the average of those tested anchors having the same wall thickness and joist orientation.

(i) Qualification tests. 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 percent of the average of the ultimate loads.

(Code 1971, § 15.10.090)

(a) Generally. In addition to the seismic analysis required elsewhere in this article, 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 with appropriate construction details shall be made part of the approved plans:

(1) a. All unreinforced masonry walls shall be anchored at the roof level by tension bolts through the wall as specified in table no. H in section 14-391 or by an approved equivalent at a maximum anchor spacing of six feet.

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 building official may require testing to verify the adequacy of the embedded ends of existing rod anchors. Tests when required shall conform to section 14-389(h).

c. When access to the exterior face of the masonry wall is prevented by proximity of an existing building, wall anchors conforming to 5 and 6 in table no. H in section 14-391 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 14-389(i).

(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 joints are supported on masonry, ledgers 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 forces specified in this article 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 (masonry cements shall not be used). 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 building official setting forth the portion of work inspected.

(6) Repair details shall be made of any cracked or damaged unreinforced masonry wall required to resist forces specified in this article.

(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) Accurately dimensioned floor plans and masonry wall elevations showing dimensioned openings, piers, wall thickness and heights.

(4) The location of cracks or damaged portions of unreinforced masonry walls requiring repairs.

(5) The type of interior wall surfaces and if reinstalling or anchoring of ceiling plaster is necessary.

(6) The general condition of the mortar joints and if the joints need pointing.

(7) The extent and type of parapet corrections which were performed in accordance with this article.

(Code 1971, § 15.10.100)

The following tables shall be used for compliance with this article:

TABLE NO. A RATING CLASSIFICATIONS

TABLE NO. B TIME LIMITS FOR COMPLIANCE

*Measured from date of building permit issuance

TABLE NO. C SERVICE PRIORITIES AND EXTENDED TIME PROVISIONS

TABLE NO. D HORIZONTAL FORCE FACTORS BASED ON RATING CLASSIFICATION

TABLE NO. E HORIZONTAL FORCE FACTORS "IS" FOR PARTS OR PORTIONS OF STRUCTURES

TABLE NO. F ALLOWABLE VALUE OF HEIGHT-TRAINING RATIO OF UNREINFORCED MASONRY WALLS WITH MAXIMUM QUALITY MORTAR (1)(2)

Notes:

(1) Minimum quality mortar shall be determined by laboratory testing in accordance with section 14-389(e).

(2) Table F is not applicable to buildings of rating classification I. Walls of buildings within rating classification I shall be analyzed in accordance with section 14-388(f).

TABLE NO. G VALUES FOR EXISTING MATERIALS

Notes:

(1) Material must be sound and in good condition.

(2) The wood lath and plaster must be reattached to existing joists or rafters in a manner approved by the building official.

(3) Stresses given may be increased for combinations of loads as specified in section 14-388(g)(2).

TABLE NO. H ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION

Notes:

(1) Bolts and dowels to be tested as specified in section 14-389(f).

(2) Bolts and dowels to be ½-inch minimum in diameter.

(3) Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools shall not be used for drilling holes or tightening anchor and shear bolt nuts.

TABLE NO. I ALLOWABLE SHEAR STRESS FOR TESTED UNREINFORCED MASONRY WALLS

* Allowable shear stress may be increased by addition of ten percent of the axial stress due to the weight of the wall directly above.