ADOPTS WITH AMENDMENTS:

CBC 2016

Heads up: There are no amended sections in this chapter.

Division 91 Earthquake Hazard Reduction in Existing Tilt-Up Concrete Wall Buildings

AMENDMENT
This section has been amended at the state or city level.

Section 91.9101 Purpose

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This section has been amended at the state or city level.
The purpose of this division is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on tilt-up concrete wall buildings designed under the building codes in effect prior to January 1, 1976. Such buildings have been categorized, based on past earthquakes, as being potentially hazardous and prone to significant damage, including possible collapse, in a moderate to major earthquake.

The provisions of this division are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury on both subject and adjacent properties and will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. The requirement for compliance with these standards does not preclude the utilization, at the building owner's option, of more extensive strengthening method that might further prevent or limit loss of life or injury or building damage. This division shall not require existing electrical, plumbing, mechanical or fire-safety systems to be altered unless they constitute a hazard to life or property.

This division provides systematic procedures and standards for identification and classification of tilt-up concrete wall building based on the current use of the building. Priorities, time periods, and standards are also established under which these buildings are required to be structurally analyzed and strengthened for seismic resistance. Where the analysis determines structural deficiencies, this division requires the building to be strengthened or demolished.

Section 91.9102 Scope

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This section has been amended at the state or city level.
The provisions of this division shall apply to all buildings designed under building codes in effect prior to January 1, 1976, which, on the effective date of this division have tilt-up concrete walls as defined herein.

Buildings within the scope of the division may not be added to or structurally altered or remodeled without first complying with the provisions of this division unless the building official determines that the alteration is minor in nature.

Seismic strengthening in place prior to the effective date of this ordinance shall be evaluated according to the provisions of this division and modified to comply if deficient.

Section 91.9103 Definitions

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This section has been amended at the state or city level.
For purposes of this division, the applicable definitions in CBC Sections 1602, 1902, 2302 and Section 11.2 of ASCE 7, and the following shall apply:

COMMENCED CONSTRUCTION. Construction pursuant to a valid building permit has progressed to the point that one of the called inspections as required by the Department has been made and the work for which the inspection has been called has been judged by the Department to be substantial and has been approved by the Department.

DEPARTMENT. The Department of Building and Safety.

ESSENTIAL BUILDING. For purposes of this division, any building housing a hospital or other medical facility having surgery or emergency treatment areas, fire or police stations, municipal government disaster operations, and communication centers.

HISTORICAL BUILDING. Any building designated or currently in the process of being designated as an historical building by an appropriate federal, state or city jurisdiction.

TILT-UP CONCRETE WALL. A form of precast concrete panel construction either cast in the horizontal position at the site and after curing, lifted and moved into place in a vertical position, or cast off-site in a fabricator's shop.

Section 91.9104 Rating Classifications

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This section has been amended at the state or city level.
The rating classification as exhibited in Table No. 91-A is hereby established and each building within the scope of this division shall be placed in one rating classification by the Department. The total occupant load as determined by CBC Section 1004.1 for the entire building plus the occupant load of any adjacent building, which interconnects with the subject building or uses the subject building for exiting purposes, shall be used to determine the rating classification.

Section 91.9105 General Requirements

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This section has been amended at the state or city level.
The owner of each building within the scope of the division shall cause an investigation of the existing construction and a structural analysis to be made of the building by a civil or structural engineer or architect licensed by the State of California, and if the building does not meet the minimum standards specified in this division, the owner shall cause it to be structurally altered to conform to such standards or cause the building to be demolished.

The owner of a building within the scope of this division shall comply with the requirements set forth above by submitting to the Department for review within 275 days after the service of the order the following:

  1. A structural analysis, subject to approval by the Department within the 275 day time period, which demonstrates that the building meets the minimum requirements of this division, or
  2. A structural analysis and plans for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or
  3. Plans for the demolition of building. After plans are submitted and approved by the Department, the owner shall obtain a building permit, commence and complete the required construction or demolition within the time limits set forth in Table No. 91-B. These time limits shall begin to run from the date the order is served in accordance with Sections 91.9106.1 and 91.9106.2 of this Code. Vacating a building shall not be deemed as complying with the requirements of this division.

Section 91.9106 Administration

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This section has been amended at the state or city level.

91.9106.1 Service of Order

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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.

Section 91.9107 Historical Buildings

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This section has been amended at the state or city level.
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.

Section 91.9108 Analysis and Design

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

AMENDMENT
This section has been amended at the state or city level.
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 specified in CBC Section 1912, using a load factor of 2.0 in lieu of 1.4 for earthquake loading, shall be used for design of embedment in concrete.

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

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This section has been amended at the state or city level.
Development of anchor loads into roof and floor diaphragms shall comply with Section 91.1615.4 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 Section 91.1615.4 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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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.

91.9108.10 Miscellaneous

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This section has been amended at the state or city level.
Existing mezzanines relying on the tilt-up walls for vertical and/or lateral support shall be anchored to the walls for the tributary mezzanine load. Walls depending on the mezzanine for lateral support shall be anchored per Sections 91.9108.1, 91.9108.2 and 91.9108.3.

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.

Section 91.9109 Materials of Construction

AMENDMENT
This section has been amended at the state or city level.
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.

Section 91.9110 Information Required on Plans

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This section has been amended at the state or city level.

91.9110.1 General

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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

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This section has been amended at the state or city level.
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:

  1. 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.

Section 91.9111 Required Building Maintenance

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This section has been amended at the state or city level.
Every building within the scope of this division which has been analyzed to demonstrate compliance or structurally altered to comply with the minimum earthquake standards in this division shall be maintained in conformity with the requirements of this division in effect at the time of such analysis or structural alteration.

Section 91.9112 Violations — Penalties for Disregarding Department Orders

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This section has been amended at the state or city level.
Notwithstanding any other provisions of this Code to the contrary, it shall be unlawful for any person, firm or corporation to maintain, use or occupy any building within the scope of this division which does not meet the minimum earthquake standards specified in this division.

Any person who violates or causes or permits another person to violate this provision is guilty of a misdemeanor. Any person includes an owner, lessor, sublessor, manager, or person in control of a building subject to this division. This term shall not include any person who is merely a tenant or other individual occupying any dwelling unit, efficiency dwelling unit, guest room or suite in a building. The legal owner of a building is that person, firm, corporation, partnership, or other entity whose name or title appears on the record with the Los Angeles County Recorder's Office, as well as all successors or assignees of these persons.

EXCEPTION: This section shall not comply if alteration or repair work has commenced in order to bring the building into compliance with requirements of this division, and such work is proceeding in accordance with the time limits set forth in any order of the department or determination of the board.

TABLE NO. 91-A
RATING CLASSIFICATIONS
Classification Occupant Load
Essential N/A
Group I 300 or more
Group II 100 to 299
Group III 50 to 99
Group IV Less than 50


TABLE NO. 91-B
TIME LIMITS FOR COMPLIANCE
Obtain Building Permit Within Commence Construction Within Complete Construction Within
365 days 545 days Three years


TABLE NO. 91-C
SERVICE PRIORITIES
Rating Classification Minimum Time Period Before Service of Order
Group I & Essential (Highest Priority) 30 days
Group II 90 days
Group III 240 days
Group IV (Lowest Priority) 1 year
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