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(Amended by Ord. No. 171,175, Eff. 7/25/96.)
91.9106.1. Service of Order. When the Department determines that a building is within the scope of this division, the owner shall comply with Section 91.9105 of this Code. If the owner does not comply, the Department shall issue an order as provided in Section 91.9106.2 to the owner of each building with the minimum time periods for service of such orders set forth in Table No. 91-C. The minimum time period for the service of such orders shall be measured from the effective date of this division.
91.9106.2. Contents of Order. (Amended by Ord. No. 172,592, Eff. 6/28/99, Oper. 7/1/99.) The order shall be in writing and may be given either by personal delivery thereof to the owner or by deposit in the United States mail in a sealed envelope, postage prepaid, addressed to the owner as shown on the last equalized assessment roll. Service by mail shall be deemed to have been completed at the time of deposit in the post office. The failure of any owner to receive such notice shall not affect in any manner the validity of any of the proceedings taken thereunder. Proof of giving any notice may be made by an affidavit of any employee of the City which shows such service in conformity with this section. Board action, Department administrative action, other correspondence between the City and the building owner or building owner’s representative, or other evidence of knowledge of notification shall also be deemed as proof of giving notice.
The order shall specify that the building has been determined by the Department to be within the scope of this division and, therefore, is required to meet the minimum seismic standards of this division. The order shall specify the rating classification of the building and shall be accompanied by a copy of Section 91.9105, which sets forth the owner’s alternatives and time limits for compliance.
91.9106.3. Appeal from Order. The owner of the building may appeal the Department’s determination that the building is within the scope of this division to the Board of Building and Safety Commissioners. Such appeal shall be filed with the Board within 60 days of the service date of the order described in Section 91.9106.2. Such appeal shall be made in writing upon appropriate forms provided therefor by the Department, and the grounds thereof shall be stated clearly and concisely. Each appeal shall be accompanied by a filing fee as set forth in Table No. 4-A of Division 4 of Article 8 of Chapter IX of the Los Angeles Municipal Code.
91.9106.4. Recordation. (Amended by Ord. No. 172,592, Eff. 6/28/99, Oper. 7/1/99.) At the time that the Department serves the aforementioned order, the Department shall file with the Office of the County Recorder a certificate stating that the subject building is within the scope of this division. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it when the Department determines the building is not in compliance with this division.
If the building is either demolished, found not to be within the scope of this division, or is structurally capable of resisting minimum seismic forces required by this division as a result of structural alterations or an analysis, the Department 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 division.
91.9106.5. Enforcement. If the owner of the subject building fails to comply with any order issued by the Department pursuant to this division within any of the time limits set forth in Section 91.9105, or within any additional time limits as may have been granted by the Board, the Department may order that the building be vacated and subsequently ordered to be demolished in accordance with the provisions of Section 91.8903 of this Code. The Superintendent of Building shall have the authority to grant two one-year extensions in cases of extreme hardship.
(Amended by Ord. No. 172,592, Eff. 6/28/99, Oper. 7/1/99.)
Qualified historical buildings may utilize alternate building standards or deviations from this division to preserve their original or restored architectural elements and features. See Section 91.8119 of this Code.
(Amended by Ord. No. 171,175, Eff. 7/25/96.)
For the purpose of this section, “anchorage system(s)” shall mean all structural elements, which supports the wall in the lateral direction, including wall anchorage and continuity tie (cross-tie) connectors in subdiaphragms and main diaphragms for retrofit and repairs.
91.9108.1. Wall Panel Anchorage. Concrete walls shall be anchored to all floors and roofs which provide lateral support for the wall. The anchorage shall provide a positive direct connection between the wall and floor or roof construction capable of resisting a horizontal force equal to 30 percent of the tributary wall weight for all buildings, and 45 percent of the tributary wall weight for essential buildings, or a minimum force of 250 pounds per linear foot of wall, whichever is greater. The required anchorage shall be based on the tributary wall panel assuming simple supports at floors and roof.
EXCEPTION: Alternate design may be approved by the Superintendent when justified by well established principles of mechanics.
91.9108.2. Special Requirements for Wall Anchors and Continuity Ties. (Amended by Ord. No. 186,488, Eff. 12/27/19.) The steel elements of the wall anchorage systems and continuity ties shall be designed by the allowable stress design method using a load factor of 1.7. The 1/3 stress increase permitted by CBC Section 1605.3.1.1 shall not be permitted for materials using allowable stress design methods.
The strength design shall be per Section 17.2.3 of ACI 318-14, unless modified by CBC Section 1905.1.8.
Wall anchors shall be provided to resist out-of-plane forces, independent of existing shear anchors.
EXCEPTION: Existing cast-in-place shear anchors may be used as wall anchors if the tie element can be readily attached to the anchors and if the engineer or architect can establish tension values for the existing anchors through the use of approved as-built plans or testing, and through analysis showing that the bolts are capable of resisting the total shear load while being acted upon by the maximum tension force due to earthquake. Criteria for analysis and testing shall be determined by the Superintendent.
Expansion anchors are not allowed without special approval of the Superintendent. Attaching the edge of plywood sheathing to steel ledgers is not considered as complying with the positive anchoring requirements of the Code; and attaching the edge of steel decks to steel ledgers is not considered as providing the positive anchorage of this Code unless testing and/or analysis are performed, which establish shear values for the attachment perpendicular to the edge of the deck.
91.9108.3. Development of Anchor Loads into the Diaphragm. (Amended by Ord. No. 186,488, Eff. 12/27/19.) Development of anchor loads into roof and floor diaphragms shall comply with LAMC Subsection 91.1613.5.3 and Section 12.11 of ASCE 7.
EXCEPTION: If continuously tied girders are present, then the maximum spacing of the continuity ties is the greater of the girder spacing or 24 feet (7315 mm).
In wood diaphragms, anchorage shall not be accomplished by use of toe nails or nails subject to withdrawal, nor shall wood ledgers, top plates or framing be used in cross-grain bending or cross-grain tension. The continuous ties required by LAMC Subsection 91.1613.5.3 and Section 12.11 of ASCE 7 shall be in addition to the diaphragm sheathing.
Lengths of development of anchor loads in wood diaphragms shall be based on existing field nailing of the sheathing unless existing edge nailing is positively identified on the original construction plans or at the site.
At reentrant corners, continuity collectors may be required for existing return walls not designed as shear walls, to develop into the diaphragm a force equal to the lesser of the rocking or shear capacity of the return wall, or the tributary shear, but not exceeding the capacity of the diaphragm. Shear anchors for the return wall shall be commensurate with the collector force. If a truss or beam, other than rafters or purlins, is supported by the return wall or by a column integral with the return wall, an independent secondary column, is required to support the roof or floor members whenever rocking or shear capacity of the return wall is governing.
Seismic deflection shall be determined at the return walls, and fins/canopies at entrances, to ensure deflection compatibility with the diaphragm, by either seismically isolating the element or attaching the element and integrating its load into the diaphragm.
91.9108.4. Anchorage at Pilasters. (Amended by Ord. No. 172,592, Eff. 6/28/99, Oper. 7/1/99.) Anchorage of pilasters shall be designed for the tributary wall anchoring load per Section 91.9108.1 of this Code, considering the wall as a two-way slab. The edge of the two-way slab shall be considered “fixed” when there is continuity at pilasters, and considered “pinned” at roof or floor levels. The pilasters or the walls immediately adjacent to the pilasters shall be anchored directly to the roof framing such that the existing vertical anchor bolts at the top of the pilasters are by-passed without causing tension or shear failure at the top of the pilasters.
EXCEPTION: If existing vertical anchor bolts at the top of the pilasters are used for the anchorage, then additional exterior confinement shall be provided.
The minimum anchorage at a floor or roof between the pilasters shall be that specified in Section 91.9108.1 of this Code.
91.9108.5. Symmetry. Symmetry of connectors in the anchorage system is required. Eccentricity may be allowed when it can be shown that all components of forces are positively resisted and justified by calculations or tests.
91.9108.6. Minimum Roof Member Size. Wood members used to develop anchorage forces to the diaphragm must be at least 3x for new construction and replacement. All such members must be checked for gravity and earthquake as part of the wall anchorage system. For existing buildings, the member check shall be without the 1/3 stress increase per Section 91.9108.2.
91.9108.7. Combination of Anchor Types. To repair and retrofit existing buildings, a combination of different anchor types of different behavior or stiffness shall not be permitted. The capacity of the new and existing connectors cannot be added.
91.9108.8. Prohibited Anchors. Usage of connectors that were bent and/or stretched from the intended use shall be prohibited.
91.9108.9. Crack and Damage Repairs, Evaluation of Existing Structural Alterations. The engineer shall report any observed structural conditions and structural damage that have imminent life safety effects on the buildings and recommend repairs. Evaluations and repairs shall be reviewed and approved by the Department. The engineer shall also evaluate the effects of alterations such as openings cut in existing wall panels without a permit, that may present immediate life safety hazard and correct when necessary.
EXCEPTION: Existing mezzanines that have independent lateral and vertical support need not be anchored to the walls.
Existing interior masonry or concrete walls not designed as shear walls, that extend to the floor above or to the roof diaphragm shall also be anchored for out-of-plane forces per Sections 91.9108.1, 91.9108.2 and 91.9108.3 of this Code. In the in-plane direction, the walls may be isolated or shall be developed into the diaphragm for a lateral force equal to the lesser of the rocking or shear capacity of the wall, or the tributary shear but not exceeding the diaphragm capacity.
(Added by Ord. No. 169,341, Eff. 2/4/94.)
All materials permitted by this Code, including their appropriate allowable stresses and those existing configurations of materials specified in Division 88 of this Code, may be utilized to meet the requirements of this division.
(Amended by Ord. No. 171,175, Eff. 7/25/96.)
91.9110.1. General. In addition to the seismic analysis required elsewhere in this division, the licensed engineer or architect responsible for the seismic analysis of the building shall record the information required by this section on the approved plans.
91.9110.2. Information Required. The plans shall accurately reflect the results of the engineering investigation and design and show all pertinent dimensions and sizes for plan review and construction. The following shall be provided:
1. Floor plans and roof plans shall show existing framing construction, diaphragm construction, proposed wall anchors, cross-ties and collectors. Existing nailing, anchors, ties and collectors shall also be shown on the plans if these are part of the design, and these structural elements need to be verified in the field.
2. At elevations where there are alterations or damage, details shall show roof and floor heights, dimensions of openings, location and extent of existing damage, and proposed repair.
3. Typical wall panel sections with panel thickness, height, location of anchors shall be provided.
4. Details shall include existing and new anchors and the method of development of anchor forces into the diaphragm framing; existing and/or new cross-ties; existing and/or new or improved support of roof and floor girders at pilasters or walls.
91.9110.3. Engineer’s or Architect’s Statement. (Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.) The responsible engineer or architect shall state on the approved plans, the following:
1. I am responsible for this building’s seismic strengthening design in compliance with the minimum seismic resistance standards of Division 91 of the Los Angeles Building Code.
and when applicable:
2. The Registered Deputy Inspector, required as a condition of the use of structural design stresses requiring continuous inspection, will be responsible to me as required by Section 91.1704 of the Los Angeles Building Code.
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