Construction documents or specifications shall be prepared for those systems and components requiring special inspection for seismic resistance as specified in CBC Section 1705.11 by the registered design professional responsible for their design and shall be submitted for approval in accordance with LAMC Subdivision 91.106.3.3. Reference to seismic standards in lieu of detailed drawings is acceptable.
The Superintendent of Building may designate certain areas of the City as "high wind velocity areas" when evidence or studies indicate that the wind velocity results in damage to structures conforming to the minimum requirements of this Code. The Superintendent of Building may specify additional requirements over and above those required by this Code with respect to the following:
- Glazing of openings in exterior walls;
- Anchorage of post and beam construction;
- Cantilever overhangs; and
- Roofing and roof framing.
The text of ASCE 7, Section 12.11.2.2.3 is modified to read as follows:
12.11.2.2.3. Wood Diaphragms. In wood diaphragms, the continuous ties shall be in addition to the diaphragm sheathing. Anchorage shall not be accomplished by use of tow nails or nails subject to withdrawal nor shall wood ledgers or framing be used in cross-grain bending or cross-grain tension. The diaphragm sheathing shall not be considered effective as providing ties or struts required by this Section.
For structures assigned to seismic Design Category D, E or F, wood diaphragms supporting concrete or masonry walls shall comply with the following:
For structures assigned to seismic Design Category D, E or F, wood diaphragms supporting concrete or masonry walls shall comply with the following:
- The spacing of continuous ties shall not exceed 40 feet. Added chords of diaphragms may be used to form subdiaphragms to transmit the anchorage forces to the main continuous crossties.
- The maximum diaphragm shear used to determine the depth of the subdiaphragm shall not exceed 75% of the maximum diaphragm shear.
The Equation 12.2-1 of ASCE 7, Section 12.12.3 is modified to read as follows:
δM = Cdδmax
The text of ASCE 7, Section 12.12.5 is modified to read as follows:
12.12.5. Deformation Compatibility for Seismic Design Category D through F. For structures assigned to Seismic Design Category D, E or F, every structural component not included in the seismic force-resisting system in the direction under consideration shall be designed to be adequate for the gravity load effects and the seismic forces resulting from displacement to the design story drift (Δ) as determined in accordance with ASCE 7 Section 12.8.6 (see also ASCE 7 Section 12.12.1).
Where determining the moments and shears induced in components that are not included in the seismic force-resisting system in the direction under consideration, the stiffening effects of adjoining rigid structural and nonstructural elements shall be considered and a rational value of member and restraint stiffness shall be used.
When designing the diaphragm to comply with the requirements stated above, the return walls and fins/canopies at entrances shall be considered. Seismic compatibility with the diaphragm shall be provided by either seismically isolating the element or by attaching the element and integrating its load into the diaphragm.
EXCEPTION: Reinforced concrete frame members not designed as part of the seismic force-resisting system shall comply with Section 21.11 of ACI 318.
Where determining the moments and shears induced in components that are not included in the seismic force-resisting system in the direction under consideration, the stiffening effects of adjoining rigid structural and nonstructural elements shall be considered and a rational value of member and restraint stiffness shall be used.
When designing the diaphragm to comply with the requirements stated above, the return walls and fins/canopies at entrances shall be considered. Seismic compatibility with the diaphragm shall be provided by either seismically isolating the element or by attaching the element and integrating its load into the diaphragm.
Modify ASCE 7 Section 12.8.1.3 as follows:
12.8.1.3. Maximum SS Value in Determination of CS and EV. The value of CS and EV are permitted to be calculated using a value of SS equal to 1.5 but not less than 70% of SDS as defined in ASCE 7 Section 11.4.4, provided that all of the following criteria are met:
- The structure does not have irregularities, as defined in ASCE 7 Section 12.3.2;
- The structure does not exceed five stories above the lower of the base or grade plane as defined in ASCE 7 Section 11.2; and, where present, each mezzanine level shall be considered a story for the purpose of this limit;
- The structure has a fundamental period, T, that does not exceed 0.5 seconds, as determined using ASCE 7 Section 12.8.2;
- The structure meets the requirements necessary for the redundancy factor p, to be permitted to be taken as 1.0, in accordance with ASCE 7 Section 12.3.4.2;
- The site soil properties are not classified as Site Classes E or F, as defined in ASCE 7 Section 11.4.2; and
- The structure is classified as Risk Category I or II, as defined in ASCE 7 Section 1.5.1.
This part contains special requirements for suspended ceilings and lighting systems. The provisions of Section 13.5.6 of ASCE 7 shall apply except as modified here.
The suspended ceilings and lighting systems shall be limited to 6 feet (1828 mm) below the structural deck unless the lateral bracing is designed by a licensed engineer or architect.
Positive bracing to the structure shall be provided at changes in the ceiling plane elevation or at discontinuities in the ceiling grid system.
Cable trays, electrical conduits and piping shall be independently supported and independently braced from the structure.
All sprinkler heads (drops), except fire-resistance-rated floor/ceiling or roof/ceiling assemblies, shall be designed to allow for free movement of the sprinkler pipes with oversize rings, sleeves or adaptors through the ceiling tile.
Sprinkler heads penetrating fire-resistance-rated floor/ceiling or roof/ceiling assemblies shall comply with CBC Section 714. Sprinkler heads and other penetrations shall have a 2 in. (50 mm) oversize ring, sleeve or adapter through the ceiling tile to allow for free movement of at least 1 in. (25 mm) in all horizontal directions. Alternatively, a swing joint that can accommodate 1 in. (25 mm) of ceiling movement in all horizontal directions is permitted to be provided at the top of the sprinkler head extension.
Sprinkler heads penetrating fire-resistance-rated floor/ceiling or roof/ceiling assemblies shall comply with CBC Section 714. Sprinkler heads and other penetrations shall have a 2 in. (50 mm) oversize ring, sleeve or adapter through the ceiling tile to allow for free movement of at least 1 in. (25 mm) in all horizontal directions. Alternatively, a swing joint that can accommodate 1 in. (25 mm) of ceiling movement in all horizontal directions is permitted to be provided at the top of the sprinkler head extension.
Suspended ceiling assemblies located along means of egress serving an occupant load of 30 or more shall comply with the following provisions:
Ceiling suspension systems shall be connected and braced with vertical hangers attached directly to the structural floor or roof system above and along the means of egress serving an occupant load of 30 or more and at lobbies accessory to Group A Occupancies. Spacing of vertical hangers shall not exceed 2 feet (610 mm) on center along the entire length of the suspended ceiling assembly located along the means of egress or at the lobby.
Independent supports and braces shall be provided for light fixtures required for exit illumination. Power supply for exit illumination shall comply with the requirements of CBC Section 1006.3.
The purpose of this section is to establish minimum regulations for the design and construction of new buildings and additions to existing buildings when constructing such buildings on or into slopes steeper than one unit vertical in three units horizontal (33.3%). These regulations establish minimum standards for seismic force resistance to reduce the risk of injury or loss of life in the event of earthquakes.
The provisions of this section shall apply to the design of the lateral-force-resisting system for hillside buildings at and below the base level diaphragm. The design of the lateral-force-resisting system above the base level diaphragm shall be in accordance with the provisions for seismic and wind design as required elsewhere in this division.
EXCEPTION: Non-habitable accessory buildings and decks not supporting or supported from the main building are exempt from these regulations.
For the purposes of this section, certain terms are defined as follows:
BASE LEVEL DIAPHRAGM is the floor at, or closest to, the top of the highest level of the foundation.
DIAPHRAGM ANCHORS are assemblies that connect a diaphragm to the adjacent foundation at the uphill diaphragm edge.
DOWNHILL DIRECTION is the descending direction of the slope approximately perpendicular to the slope contours.
FOUNDATION is concrete or masonry, which supports a building, including footings, stem walls, retaining walls, and grade beams.
FOUNDATION EXTENDING IN THE DOWNHILL DIRECTION is a foundation running downhill and approximately perpendicular to the uphill foundation.
HILLSIDE BUILDING is any building or portion thereof constructed on or into a slope steeper than one unit vertical in three units horizontal (33.3%). If only a portion of the building is supported on or into the slope, these regulations apply to the entire building.
PRIMARY ANCHORS are diaphragm anchors designed for and providing a direct connection as described in LAMC Subdivision 91.1613.9.5 and Paragraph 91.1613.9.7.3 between the diaphragm and the uphill foundation.
SECONDARY ANCHORS are diaphragm anchors designed for and providing a redundant diaphragm to foundation connection, as describe in LAMC Subdivision 91.1613.9.6 and Paragraph 91.1613.9.7.4.
UPHILL DIAPHRAGM EDGE is the edge of the diaphragm adjacent and closest to the highest ground level at the perimeter of the diaphragm.
UPHILL FOUNDATION is the foundation parallel and closest to the uphill diaphragm edge.
DIAPHRAGM ANCHORS are assemblies that connect a diaphragm to the adjacent foundation at the uphill diaphragm edge.
DOWNHILL DIRECTION is the descending direction of the slope approximately perpendicular to the slope contours.
FOUNDATION is concrete or masonry, which supports a building, including footings, stem walls, retaining walls, and grade beams.
FOUNDATION EXTENDING IN THE DOWNHILL DIRECTION is a foundation running downhill and approximately perpendicular to the uphill foundation.
HILLSIDE BUILDING is any building or portion thereof constructed on or into a slope steeper than one unit vertical in three units horizontal (33.3%). If only a portion of the building is supported on or into the slope, these regulations apply to the entire building.
PRIMARY ANCHORS are diaphragm anchors designed for and providing a direct connection as described in LAMC Subdivision 91.1613.9.5 and Paragraph 91.1613.9.7.3 between the diaphragm and the uphill foundation.
SECONDARY ANCHORS are diaphragm anchors designed for and providing a redundant diaphragm to foundation connection, as describe in LAMC Subdivision 91.1613.9.6 and Paragraph 91.1613.9.7.4.
UPHILL DIAPHRAGM EDGE is the edge of the diaphragm adjacent and closest to the highest ground level at the perimeter of the diaphragm.
UPHILL FOUNDATION is the foundation parallel and closest to the uphill diaphragm edge.
Every hillside building within the scope of this division shall be analyzed, designed and constructed in accordance with provisions of this division. When the code-prescribed wind design produces greater effects, the wind design shall govern, but detailing requirements and limitations prescribed in this and referenced sections shall be followed.
The following provisions shall apply to the seismic analysis and design of the connections for the base level diaphragm in the downhill direction.
For seismic forces acting in the downhill direction, the base of the building shall be the floor at, or closest to, the top of the highest level of the foundation.
A primary anchor and diaphragm strut shall be provided in line with each foundation extending in the downhill direction. Primary anchors and diaphragm struts shall also be provided where interior vertical lateral-force-resisting elements occur above and in contact with the base level diaphragm. The spacing of primary anchors and diaphragm struts or collectors shall in no case exceed 30 feet (9144 mm).
Primary anchors and diaphragm struts shall be designed in accordance with the requirements of LAMC Subdivision 91.1613.9.8.
The following lateral-force-resisting elements shall not be designed to resist seismic forces below the base level diaphragm in the downhill direction:
- Wood structural panel wall sheathing,
- Cement plaster and lath,
- Gypsum wallboard, and
- Tension only braced frames.
Secondary anchors at the base level diaphragm shall be designed for a minimum force equal to the base shear, including forces tributary to the base level diaphragm, but not less than 600 pounds per lineal foot (8.76 kN/m). The secondary anchors shall be uniformly distributed along the uphill diaphragm edge and shall be spaced a maximum of four feet (1219 mm) on center.
Secondary anchors and diaphragm struts shall be designed in accordance with LAMC Subdivision 91.1613.9.8.
The following provisions shall apply to the lateral analysis and design of the connections for all diaphragms below the base level diaphragm in the downhill direction.
The design force described in LAMC Paragraph 91.1613.9.7.2 shall be resisted through primary anchors from diaphragm struts provided in each diaphragm to the foundation. Primary anchors shall be provided and designed in accordance with the requirements and limitations of LAMC Subdivision 91.1613.9.5.