Chapter 15.24
EARTHQUAKE HAZARD REDUCTION CODE
Sections:
15.24.050 Rating classification.
15.24.060 General requirements.
15.24.080 Violations—Penalties.
15.24.090 Analysis and design.
15.24.100 Materials of construction.
15.24.110 Information required on plans.
15.24.010 Short title.
This chapter shall be known and referred to as the “earthquake hazard reduction code of the city of San Jacinto.” (Ord. 977 (part), 1993: prior code § 15.17.010)
15.24.020 Purpose.
The purpose of this chapter 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 prior to 1934 (the adoption date of the Building Code requiring earthquake resistant design of buildings). Such buildings have been widely recognized for sustaining life-hazardous damage, including partial or complete collapse during moderate to strong earthquakes.
The provisions of this chapter are intended as minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury. Compliance with these standards will not necessarily prevent loss of life or injury or prevent earthquake damage to rehabilitated buildings. This chapter does not require alteration of existing electrical, plumbing, mechanical or fire safety systems unless they constitute a hazard to life or property.
This chapter provides systematic procedures and standards for identification and classification of unreinforced masonry bearing wall buildings 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 finds deficiencies, this chapter requires the building to be strengthened or demolished.
Qualified historical buildings shall comply with the State Historical Building Code (SHBC) established under Part 8, Title 24 of the California Administrative Code. (Ord. 977 (part), 1993: prior code § 15.17.020)
15.24.030 Scope.
The provisions of this chapter shall apply to all buildings constructed or under construction prior to October 6, 1933 (adoption date of local earthquake resistant code requirements), or for which a building permit was issued prior to October 6, 1933, which on the effective date of the ordinance codified in this chapter have unreinforced masonry bearing walls as defined herein or any other building found to have unreinforced masonry bearing walls.
Exception: This chapter 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. (Ord. 977 (part), 1993: prior code § 15.17.030)
15.24.040 Definitions.
For purposes of this chapter, the applicable definitions in Sections 2302 and 2312 of the Uniform Building Code shall apply:
“Essential building” means any building housing a hospital or other medical facility having surgery or emergency treatment areas; fire or police station; municipal government disaster operation and communication centers.
“High risk building” means any building, not classified as an essential building, having an occupant load of one hundred (100) or more, as determined by Section 3302(a) U.B.C.
Exception: A high risk building shall not include the following:
1. Any building having exterior walls braced with masonry crosswalks or wood frame crosswalks spaced less than forty (40) feet apart in each story. Crosswalks shall be full story height with a minimum length of one and one-half times the story height.
2. Any building used for its intended purpose, as determined by the building official, for less than twenty (20) hours per week.
“Low risk building” means any building, not classified as an essential building, having an occupant load of less than twenty (20) occupants as determined by Section 3302(a) U.B.C.
“Medium risk building” means any building, not classified as a high risk building or an essential building, having an occupant load of twenty (20) occupants or more as determined by Section 3302(a) U.B.C.
“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 one hundred (100) pounds per linear foot;
3. The area of reinforcing steel is less than fifty (50) percent of that required by Section 2407(h) U.B.C., 1991 Edition. (Ord. 977 (part), 1993: prior code § 15.17.040)
15.24.050 Rating classification.
The rating classifications shown in Table A are established and each building within the scope of this chapter shall be placed in one such rating classification by the building official. The total occupant load of the entire building as determined by Section 3302(a) U.B.C. shall be used to determined the rating classification.
Exception: For the purpose of this chapter, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications. (Ord. 977 (part), 1993: prior code § 15.17.050)
15.24.060 General requirements.
The owner of each building within the scope of this chapter shall cause a structural analysis of the building to be made by a civil or structural engineer or architect licensed by the state of California. If the building does not meet the minimum earthquake standards specified in this chapter, the owner shall either cause it to be structurally altered to conform the such standards; or cause the building to be demolished.
The owner of a building within the scope of this chapter shall comply with the requirements set forth above by submitting to the building official for review within the stated time limits:
A. Within two hundred seventy (270) days after the service of the order, a structural analysis, which is subject to approval by the building official, and which shall demonstrate that the building meets the minimum requirements of this chapter; or
B. Within two hundred seventy (270) days after the service of the order, the structural analysis and plans for the proposed structural alterations of the building necessary to comply with the minimum requirements of this chapter; or
C. Within one hundred twenty (120) days after service of the order, plans for the installation of wall anchors in accordance with the requirements specified in Section 15.24.080; or
D. Within two hundred seventy (270) days after the service of the order, plans for the demolition of the building.
After 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 B. These time limits shall begin to run from the date the order is served in accordance with Section 15.24.070(A) and (B).
Owners electing to comply with subsection C of this section are also required to comply with subsections B or D of this section provided, however, that the two hundred seventy (270) day period provided for in such subsections B and D 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 shall be extended in accordance with Table C. 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 15.24.070(B). The time limit for commencing construction shall commence from the date the building permit is issued. (Ord. 977 (part), 1993: prior code § 15.17.060)
15.24.070 Administration.
A. Service of Order. The building official shall issue and order, as provided in subsection B of this section to the owner of each building within the scope of this chapter in accordance with the minimum time periods for service of such orders set forth in Table C. Upon receipt of a written request from the owner, the building official shall order a building to comply prior to the normal service date for such building set forth in this section.
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 building official to be within the scope 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 Section 15.24.060 which sets forth the owner’s alternatives and time limits for compliance.
C. Appeal From Order. The owner or person in charge or control of the building may appeal to the city manager, the building official’s initial determination that the building is within the scope of this chapter. Such appeal shall be filed with the board within sixty (60) days from the service date of the order described in subsection B of this section. Any such appeal shall be decided by the board no later than sixty (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 shall be accompanied by a filing fee as set forth in the code.
Appeals or requests for slight modifications from any other determinations, orders or actions by the building official pursuant to this chapter, shall be made in accordance with the normal appeal procedures established in this code.
D. Recordation. At the time that the aforementioned order is served, the building official shall file with the office of the county recorder a certificate stating that the subject building is within the scope of this chapter. 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 it is not found to comply with this chapter.
If the building is found not to be within the scope of this chapter, or as a result of structural alterations or an analysis is found to be structurally capable of resisting minimum seismic forces required by this chapter; or is demolished; the building official shall file with the office of the county recorder a certificate terminating the status of the subject building as being classified within the scope of this chapter.
E. Enforcement. If the owner or other person in charge or control of the subject building fails to comply with any order issued by the building official pursuant to this chapter within any of the time limits set forth in Section 15.24.060 the building official shall order the entire building vacated and remain vacated until such order has been complied with. If compliance with such order has not been accomplished within ninety (90) days after the date the building has been ordered vacated, or by such additional time as may have been granted, the building official may order demolition of the building in accordance with the Abatement of Dangerous Buildings provisions of this code. (Ord. 977 (part), 1993: prior code § 15.17.070)
15.24.080 Violations—Penalties.
A. Violation Prohibited. No person, firm, partnership, association or corporation shall violate any provisions of this chapter and any provision of the codes, rules or regulations adopted in this chapter.
B. Criminal Penalties. Any person, firm, partnership, association or corporation violating any of the provisions of this chapter or provisions of the codes, rules or regulations adopted in this chapter by reference is guilty of a misdemeanor and upon conviction thereof, shall be punishable by a fine of not more than five hundred dollars ($500.00) or by imprisonment for a period of not more than six months, or by both such fine and imprisonment.
C. Continuing Violation. Every person, firm, partnership, association or corporation violating any of the provisions, of this chapter or provisions of the codes, rules of regulations adopted in this chapter by reference is guilty of a separate offense for each day or portion thereof during which such violation continues and shall be punishable thereof as provided in this chapter. (Ord. 977 (part), 1993: prior code § 15.17.080)
15.24.090 Analysis and design.
A. General. Every structure within the scope of this chapter 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:
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V=ZIKCSW |
Formula (1) |
The value of IKCS need not exceed the values set forth in Table D based on the applicable rating classification of the building.
B. Lateral Forces on Elements of Structures. Parts of portions of structures shall be analyzed and designed for lateral loads in accordance with subsections 15.24.090(A) of this chapter and 2312(e) of the Uniform Building Code but not less than the value from the following equation:
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Fp=ZICp SWp |
Formula (2) |
For the provisions of this subsection, the product of IS need not exceed the values as set forth in Table E.
Exception: Unreinforced masonry walls in buildings not having a rating classification of I may be analyzed in accordance with Section 15.24.100.
The value of Cp need not exceed the values set forth in Table F.
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 and the equation Fp=ZICpSWp ad modified by Table E. Minimum anchorage of masonry walls to each floor or roof shall resist a minimum force of two hundred (200) pounds per linear foot acting normal to the wall at the level of the floor or roof.
D. Level or Required Repair. Alterations and repairs required to meet the provisions of this chapter shall comply with all other applicable requirements of the Uniform Building Code unless otherwise 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 existing structures within the scope of this chapter shall be in accordance with the analysis specified in Chapter 23 of the U.B.C.
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. 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 Uniform Building Code and those materials and types of construction specified in Section 15.24.100.
2. Connections. Materials and connectors used for interconnection of parts and portions of the structure shall conform to the Uniform Building Code. Nails may be used as part of an approved connector.
3. Unreinforced Masonry Walls. Except as modified herein, unreinforced masonry walls shall be analyzed as specified in Sections 2406, 2407 and 2408 of the U.B.C. to withstand all vertical loads as specified in Chapter 23 of the Uniform Building Code in addition to the seismic forces required by this chapter. The fifty (50) percent increase in the seismic force factor for shear walls as specified in Section 2407(h) 4F of the Uniform 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 chapter shall be strengthened or shall be removed and replaced.
Exceptions:
1. Unreinforced masonry walls in buildings not classified as a Rating Classification I pursuant to Table A may be analyzed in accordance with Section 15.24.100.
2. 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 2303(f) of the U.B.C.
2. Existing Materials. When stresses in existing lateral force resisting elements are due to a combination of dead loads plus live load plus seismic loads, the allowable working stress specified in the Uniform Building Code may be increased one hundred (100) percent. However, no increase will be permitted in the stresses allowed in Section 15.24.100 and the stressed in members due only to seismic and dead loads shall not exceed the values permitted by Section 2303(d) of the Uniform Building Code.
3. Allowable Reduction of Bending Stress by Vertical Load. 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. (Ord. 977 (part), 1993: prior code § 15.17.090)
15.24.100 Materials of construction.
A. General. All materials permitted by the Uniform Building 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. Unreinforced masonry walls analyzed in accordance with this section may provide vertical support for roof and floor construction and resistance to lateral loads. The facing and backing of such walls shall be bonded so that not less than four percent of the exposed face area is composed of solid headers extending not less than four inches into the backing. The distance between adjacent full-length headers shall not exceed twenty-four (24) inches vertically or horizontally. Where the backing consists of two or more wythes the header shall extend not less than four inches into the most distant wythe, or the backing wythes shall be bonded together with separate headers whose area and spacing conform to the foregoing.
Tension stresses due to seismic forces normal to the wall may be neglected if the walls do not exceed the height to thickness ration in Table G and the in-plane shear stresses due to seismic loads as set forth in Table J.
If the wall height-thickness ration exceeds the specified limits, the wall may be supported by vertical bracing members designed in accordance with Section 15.24.090. 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 15.24.090(B) if the deflection at design loads is not less than one-quarter nor more than one-third of the wall thickness.
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.
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 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.
D. Alternate Materials. Alternate materials, designs and methods of construction may be approved by the building official in accordance with the provisions of the Uniform Building Code.
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 building official. 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 leaned to remove loose and deteriorated mortar. Mortar for pointing shall be Type S or N except that 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 shall be kept of all such tests and of their locations in the building, 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 one thousand five hundred (1500) 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 eighty (80) percent of the shear tests shall not be less than the total of thirty (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 fifteen (15) degrees from the axis of the applied load. The mortar joint tested in shear shall have an average ultimate stress of twenty (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 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 special inspector using a torque calibrated wrench to the following minimum torques:
1/2” diameter bolts or dowels = 40 foot-lbs.
5/8” diameter bolts or dowels = 50 foot-lbs.
3/4” 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 when bearing on steel.
G. Determination of Allowable Stresses for Design Methods Based on Test Results.
1. Design Shear Values. Design seismic in-plane shear stresses shall be substantiated by tests performed as specified in subsection (E)(3) and (4) of this section.
Design stresses shall be related to test results obtained in accordance with Table J.
Intermediate values between three and ten psi may be interpolated.
2. Design Compression and Tension Values. Compression stresses from unreinforced masonry having a minimum design shear value of three psi shall not exceed one hundred (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 three hundred (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 forty (40) percent 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 twenty (20) percent of the average of the ultimate loads. (Ord. 977 (part), 1993: prior code § 15.17.100)
15.24.110 Information required on plans.
A. General. In addition to the seismic analysis required elsewhere in 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:
1. All unreinforced masonry walls shall be anchored at the roof level by tension bolts through the wall as specified in Table I, or by approved equivalent at a maximum anchor spacing of six feet.
All unreinforced masonry walls shall be anchored at all floors with tension bolts through the wall or by existing rod anchors at the 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 15.24.100(H).
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 may be used.
Alternative devices to be used in lieu of tension bolts for masonry wall anchorage shall be tested as specified in Section 15.24.100(1).
2. Diaphragm chord stressed of horizontal diaphragms shall be developed in existing materials or by addition of new materials.
3. Where trussed and beams other than rafters or joists 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 the forces specified in this chapter shall be removed, stabilized or braced to insure 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 special 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 prepared for 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, if any, which were performed in accordance with the Uniform Building 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 whether reinstalling or anchoring of ceiling plaster is necessary;
7. The general condition of the mortar joints and whether the joints need pointing;
8. Site plan. (Ord. 977 (part), 1993: prior code § 15.17.110)
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Table A RATING CLASSIFICATION |
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Type of Building |
Classifications |
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Essential Building |
I |
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High Risk Building |
II |
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Medium Risk Building |
III |
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Low Risk Building |
IV |
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Table B TIME LIMITS FOR COMPLIANCE(1) |
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Commence |
Complete |
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Required Action |
Obtain Building |
Construction |
Construction |
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By Owner |
Permit Within |
Within |
Within |
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Complete Structural Alterations or Building Demolition |
1 year |
180 days(2) |
3 years or Building Demolition |
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Wall Anchor Installation |
180 days |
270 days |
1 year |
(1) Where two or more buildings under separate ownership are to be rehabilitated simultaneously, an extension can be based on the average time requirements for the buildings involved, with a suggested minimum extension of 6 months. An extension could be granted on submission of a binding agreement between the owners involved, with the actual date of compliance to be determined by the building official.
(2) Measured from date of building permit issuance. All the other time limits are measured from the date of the order.
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Table C SERVICE PRIORITIES AND EXTENDED TIME PROVISIONS |
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Rating Classification |
Occupant Load |
Extension of Time if Wall Anchors are Installed |
Minimum Time Periods for Service of Order |
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I (Highest Priority) |
Any |
1 year |
0 |
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II |
100 or more |
3 years |
90 days |
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100 or more |
5 years |
1 year |
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III |
51 to and including 99 |
6 years |
2 years |
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20 to and including 50 |
6 years |
3 years |
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IV (Lowest Priority) |
Less than 20 |
7 years |
4 years |
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Table D HORIZONTAL FORCE FACTORS BASED ON RATING CLASSIFICATION |
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Rating Classification |
IKCS |
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I |
0.186 |
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II |
0.133 |
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III & IV |
0.100 |
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Table E HORIZONTAL FORCE FACTORS “IS” FOR PARTS OR PORTIONS OF STRUCTURES |
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Rating Classification |
IS |
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I |
1.50 |
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II |
1.00 |
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III & IV |
0.75 |
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Table F HORIZONTAL FORCE FACTOR “Cp” FOR PARTS OR PORTIONS OF BUILDINGS OR OTHER STRUCTURES(1) |
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Part or Portion of Buildings |
Direction of Force |
Value of Cp |
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Exterior bearing and non-bearing walls, interior bearing walls and partitions, interior non-bearing walls and partitions overten feet in height, masonry fences over six feet in height. |
Normal to Flat Surface |
0.20 |
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Cantilever parapet and other cantilever walls, except retaining walls. |
Normal to Flat Surface |
1.00 |
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Exterior and interior ornamentations and appendages. |
Any Direction |
1.00 |
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When connected to or a part of a building: towers, tanks, towers and tanks plus contents, racks over 8 feet 3 inches in height plus contents, chimneys, smokestacks, and penthouses. |
Any Direction |
0.20(2)(4) |
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When connected to or a part of a building: rigid and rigidly mounted equipment and machinery not required for continued operation of essential occupancies. (5) |
Any Horizontal Direction |
0.201(3) |
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Tanks plus effective contents resting on the ground. |
Any Direction |
0.12 |
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Floors and roofs acting as diaphragms. |
In the plane of the diaphragm |
0.12(6) |
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Prefabricated structural elements, other than walls, withforce applied at center of gravity of assembly. |
Any Horizontal Direction |
0.30 |
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Connections for exterior panels or elements. |
Any Direction |
2.00 |
(1) See Section 15.24.090(B) for use of Cp.
(2) When located in the upper portion of any building with a hn/D ratio of 5 to 1 or greater the value shall be increased by 50 percent.
(3) For flexible and flexibly mounted equipment and machinery, the appropriate values for Cp shall be determined with consideration given to both the dynamic properties of the equipment and machinery and to the building or structure in which it is placed.
(4) The Wp for storage racks shall be the weight of the racks plus contents. The value of Cp for racks over two storage support levels in height shall be 0.16 for the levels below the top two levels.
(5) The design of the equipment and machinery and their anchorage is an integral part of the design and specification of such equipment and machinery. The structure to which the equipment or machinery is mounted shall be capable of resisting the anchorage forces (see also Section 2312(g)4 of the U.B.C.).
(6) Floor and roofs acting as diaphragms shall be designed for a minimum force resulting from a Cp of .12 applied to Wp unless a greater force results from the distribution of lateral forces in accordance with Section 2312(e) of the U.B.C.
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Table G ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS WITH MINIMUM QUALITY MORTAR.(1)(2) |
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Building with Crosswalks Defined by Section 15.24.040 |
All Other Buildings |
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Walls of One-Story Buildings |
16 |
13 |
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First Story Wall of Multi-Story Buildings |
16 |
15 |
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Walls in Top Story of Multi-Story Buildings |
14 |
9 |
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All Other Walls |
16 |
13 |
(1) Minimum quality mortar shall be determined by laboratory testing in accordance with Section 15.24.100(E).
(2) Table G is not applicable to buildings of rating classification I. Walls of buildings within rating classification I shall be analyzed in accordance with Section 15.24.090(F).
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Existing Materials or Configuration of Materials(1) |
Allowable Values |
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1. Horizontal Diaphragms. |
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a. Roofs with straight sheathing and roofing applied directly to the sheathing. |
100 lbs. per foot for seismic shear |
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b. Roofs with diagonal sheathing and roofing applied directly to the sheathing. |
400 lbs. per foot for seismic shear |
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c. Floors with straight tongue and groove sheathing. |
150 lbs. per foot for seismic shear |
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d. Floors with straight sheathing and finished wood flooring. |
300 lbs. per foot for seismic shear |
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e. Floors with diagonal sheathing and finished wood flooring. |
450 lbs. per foot for seismic shear |
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f. Floors or roofs with straight sheathing and plaster applied to the joist or rafters (2) |
Add 50 lbs. per foot to the allowable values for Items la and lc. |
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2. Shear Walls. |
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Wood stud walls with lath and plaster. |
100 lbs. per foot each side for seismic shear |
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3. Plain Concrete Footings. |
f'c = 1500 psi unless otherwise shown by tests. |
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4. Douglas Fir Wood. |
Allowable stress same as No. 1 D.F. (3) |
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5. Reinforcing Steel. |
ft = 18,000 lbs. per square inch max. (3) |
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6.Structural Steel. |
ft = 20,000 lbs. per square inch max. |
(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 Department.
(3) Stresses given may be increased for combinations of loads as specified in Section 15.24.090(G)(2).
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Table I ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION |
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New Materials or Configuration of Materials |
Allowable Values |
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1. Horizontal Diaphragms. Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing joists or rafters and edges of plywood located on center of individual sheathing boards. |
Same as specified in Table No. 25-J-1 of this is Code for on blocked diaphragms.* |
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2. Shear Walls |
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a. Plywood sheathing applied directly over existing wood studs. No value shall be given to plywood applied over existing plaster or wood sheathing. |
Same as values specified in Table No. 25-K-1 for shear walls. |
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b. Drywall or plaster applied directly over existing wood studs. |
75% of the value as specified in Table 47-I. |
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c. Drywall or plaster applied to plywood sheathing over existing wood studs. |
33 1/3 per cent of the values specified in Table No. 47-1. |
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3. Shear Bolts. |
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Shear bolts and shear dowels embedded a minimum of 8 inches into unreinforced masonry walls. Bolt centered in a 2 1/2 inch diameter hole with dry-pack or non-shrink grout around circumference of bolt or dowel.1 |
100% of the values for solid masonry specified in Table 24E. No values larger than those 3/4 inch bolts shall be used. |
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4. Tension Bolts. |
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Tension bolts and tension dowels extending entirely through unreinforced masonry walls secured with bearing plates on far side of wall with at least 30 sq. inches of area.2 |
1200 lbs. per bolt or dowel. |
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5. Wall Anchors 15.24.110(B). |
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Bolts extending to the exterior face of the wallwith a 2 1/2 inch round plate under the head. Installed as specified for shear bolts. Spaced not closer than 12 inches on centers.1,2 |
600 lbs. per bolt. |
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6.Wall Anchors. |
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Bolts or dowels extending to the exterior face of the wall with a 2 1/2 inch round plate under the head and drill at an angle of 22 1/2 degrees to the horizontal. Installed as specified for shear bolts.1,2 |
1200 lbs. per bolt. |
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7. Infilled Walls. |
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Reinforced masonry infilled openings in existing unreinforced masonry walls with keys or dowels to match reinforcing. |
Same as values specified for unreinforced masonry walls. |
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8. Reinforced Masonry. |
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Masonry piers and walls reinforced per Section 2407 of the U.B.C. |
Same as values specified in Division 26, UBC |
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9. Reinforced Concrete. |
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Concrete footings, walls and piers reinforced as specified in Division 26 of the U.B.C. and designed for tributary loads. |
Same as values specified in Division 26, UBC |
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10. Existing Foundation Loads. |
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Foundation loads for structures exhibiting no evidence of settlement. |
Calculated existing foundation loads due to maximum dead load plus live load may be increased by 25% for dead load, and may be increased 50% for dead load plus seismic load required by this Division. |
NOTES:
1 Bolts and dowels to be tested as specified in Section 15.24.100(F).
2 Bolts and dowels to be 1/2 inch minimum in diameter.
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Eighty percent of test resultsin psi not less than |
Average test results of cores in psi |
Seismic in-plane shear based on gross area(1) |
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30 plus axial stress |
20 |
3 psi |
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40 plus axial stress |
27 |
4 psi |
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50 plus axial stress |
33 |
5 psi |
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100 plus axial stress or more |
67 or more |
10 psi max |
(1) Allowable shear stress may be increased by addition of 10 percent of the axial stress due to the weight of the wall directly above.
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Glossary of Symbols and Notations |
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C |
= |
Numerical coefficient as specified in Section 2312(d) of the U.B.C. |
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Cp |
= |
Numerical coefficient as specified in Section 2312(h) of the U.B.C. and as set forth in Table No. 23-J |
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D |
= |
The dimension of the structure, in feet, in a direction parallel to the applied forces |
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f'c |
= |
Specified compressive strength of concrete, psi |
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Fp |
= |
Lateral forces on a part of the structure and in the direction under consideration |
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ft |
= |
Allowable tensile stress, psi |
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hn |
= |
Height in feet above the base to level n |
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I |
= |
Occupancy Importance Factor as set forth in Table No. 23-K |
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S |
= |
Numerical coefficient for site-structure resonance |
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V |
= |
The total lateral force or shear at the base |
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W |
= |
The total dead load as defined in Section 2302 of the U.B.C. including the partition loading specified in Section 2304(d) of the U.B.C. where applicable |
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Wp |
= |
The weight of a portion of a structure or nonstructural component |
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Z |
= |
Numerical coefficient dependent upon the zone as determined by Figure No. 1, of Chapter 23. All areas in California are classified in Zones 3 or 4. For locations in Zone No. 3, Z = 3/4. For locations in Zone No. 4, Z = 1 |