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(Amended by Ord. No. 182,850, Eff. 1/3/14.)
91.2204.1. Welding. The details of design, work quality and technique for welding, inspection of welding and qualification of welding operators shall conform to the requirements listed in CBC Sections 2205, 2206, 2207, 2208, 2209, 2210 and 2211. Special inspection of welding shall be provided where required by CBC Section 1705. (Amended by Ord. No. 184,692, Eff. 12/30/16.)
All welding, except when performed at the shop of an approved fabricator, shall be done by operators certified by the Department for the type of operation involved in accordance with the provisions of CBC Section 1705.2.2.1.
Complete details of location, type, size and amount of all welds shall be clearly shown on the plans. Where symbols are used on the plans, they shall be the "Standard Welding Symbols," AWS A 2.4, of the American Welding Society (AWS). When it is necessary to use a special erection sequence of welding to minimize locked-up stresses or distortion, the Department may require the erection sequence of welding to be shown on the plans.
Welding procedures are qualified if they are in accordance with the AWS. Other welding procedures require special qualification approval by the Department. Each application for a special qualification shall be accompanied by a fee of $50.00.
Section F2.5b(4) - The use of rectangular HSS are not permitted for bracing members, unless filled solid with cement grout having a minimum compressive strength of 3000 psi (20.7 MPa) at 28 days. The effects of composite action in the filled composite brace shall be considered in the sectional properties of the system where it results in the more severe loading condition or detailing.
(Division Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.)
Section
91.2300 Basic Provisions.
91.2301 General.
91.2304 General Construction Requirements.
91.2305 General Design Requirements for Lateral Force-Resisting System.
91.2306 Allowable Stress Design.
91.2308 Conventional Light-Frame Construction.
(Amended by Ord. No. 185,587, Eff. 7/16/18.)
Section 2301 of the CBC is adopted by reference, except Section 2301.1 of the CBC is not adopted; and, in lieu, LAMC Subsection 91.2301.1 is added.
Hillside buildings (buildings constructed upon slopes steeper than one unit vertical in three units horizontal [33.3% slope]) shall comply with LAMC Subsection 91.1613.9 (seismic design provisions for hillside buildings) and this division.
(Amended by Ord. No. 187,719, Eff. 1/23/23.)
Section 2304 of the CBC is adopted by reference, except Section 2304.10.2 and 2304.12.2.8 of the CBC are not adopted; and, in lieu, LAMC Subsections 91.2304.10.2 and 91.2304.12.2.8 are added.
91.2304.10.2. Fastener Requirements. Connections for wood members shall be designed in accordance with the appropriate methodology in CBC Section 2302.1. The number and size of fasteners connecting wood members shall not be less than that set forth in Table 2304.10.2. Staple fasteners in Table 2304.10.2 shall not be used to resist or transfer seismic forces in structure assigned to Seismic Design Category D, E, or F.
EXCEPTION: Staples may be used to resist or transfer seismic forces when the allowable shear values are substantiated by cyclic testing and approved by the Superintendent of Building.
91.2304.12.2.8. Wood Used In Retaining Walls and Cribs. Wood installed in retaining or crib walls shall be preservative treated in accordance with AWPA U1 (Commodity Specifications A or F) for soil and fresh water use. Wood shall not be used in retaining walls or cribs for structures assigned to Seismic Design Category D, E or F.
(Amended by Ord. 181,758, Eff. 8/8/11.)
91.2305.4. Quality of Nails. In Seismic Design Category D, E or F, mechanically driven nails used in wood structural panel shear walls shall meet the same dimensions as that required for hand-driven nails, including diameter, minimum length and minimum head diameter. Clipped head or box nails are not permitted in new construction. The allowable design value for clipped head nails in existing construction may be taken at no more than the nail-head-area ratio of that of the same size hand-driven nails.
91.2305.5. Hold-down Connectors. In Seismic Design Category D, E or F, hold-down connectors shall be designed to resist shear wall overturning moments using approved cyclic load values or 75 percent of the allowable seismic load values that do not consider cyclic loading of the product. Connector bolts into wood framing shall require steel plate washers on the post on the opposite side of the anchorage device. Plate size shall be a minimum of 0.229 inch by 3 inches by 3 inches (5.82 mm by 76 mm by 76 mm) in size. Hold-down connectors shall be finger tight and ½ turn just prior to covering the wall framing.
(Amended by Ord. No. 182,850, Eff. 1/3/14.)
91.2306.2. Wood-Frame Diaphragms. (Amended by Ord. No. 185,587, Eff. 7/16/18.) Wood-frame diaphragms shall be designed and constructed in accordance with AWC SDPWS. Where panels are fastened to framing members with staples, requirements and limitations of AWC DPWS shall be met and the allowable shear values set forth in CBC Table 2306.2(1) or 2306.2(2) shall only be permitted for structures assigned to Seismic Design Category A, B or C.
EXCEPTION: Allowable shear values where panels are fastened to framing members with staples may be used if such values are substantiated by cyclic testing and approved by the building official.
The allowable shear values of CBC Tables 2306.2(1) and 2306.2(2) are permitted to be increased 40% for wind design.
Wood structural panel diaphragms used to resist seismic forces in structures assigned to Seismic Design Category D, E or F shall be applied directly to the framing members.
EXCEPTION: Wood structural panel diaphragm is permitted to be fastened over solid lumber planking or laminated decking, provided the panel joints and lumber planking or laminated decking joints do not coincide.
91.2306.3. Wood-Frame Shear Walls. (Amended by Ord. No. 186,488, Eff. 12/27/19.) Wood-frame shear walls shall be designed and constructed in accordance with AWC SDPWS. For structures assigned to Seismic Design Category D, E, or F, application of Tables 4.3A and 4.3B of AWC SDPWS shall include the following:
1. Wood structural panel thickness for shear walls shall not be less than 3/8 inch (9.525 mm) thick, and studs shall not be spaced at more than 16 inches (406.4 mm) on center.
2. The maximum nominal unit shear capacities for three-ply plywood resisting seismic forces in structures assigned to Seismic Design Category D, E or F is 400 pounds per linear foot (plf) (181.43 kg per meter).
3. Where shear design values using allowable stress design (ASD) exceed 350 plf or load and resistance factor design (LRFD) exceed 500 plf, all framing members receiving edge nailing from abutting panels shall not be less than a single 3 inch (76.19 mm) nominal member, or two 2 inch (50.8 mm) nominal members fastened together in accordance with CBC Section 2306.1 to transfer the design shear value between framing members. Wood structural panel joint and sill plate nailing shall be staggered at all panel edges. See Sections 4.3.6.1 and 4.3.6.4.3 of AWC SDPWS for sill plate size and anchorage requirements.
4. Nails shall be placed not less than 1/2 inch (12.7 mm) in from the panel edges and not less than 3/8 inch (9.525 mm) from the edge of the connecting members for shear greater than 350 plf using ASD or 500 plf using LRFD. Nails shall be placed not less than 3/8 inch (9.525 mm) from panel edges and not less than 1/4 inch (6.35 mm) from the edge of the connecting members for shears of 350 plf or less using ASD or 500 plf or less using LRFD.
5. Table 4.3B of AWC SDPWS application is not allowed for structures assigned to Seismic design category D, E or F.
For structures assigned to Seismic Design Category D, Application of Table 4.3C of AWC SDPWS shall not be used below the top level in a multi-level building for structures.
Where panels are fastened to framing members with staples, requirements and limitations of AWC SDPWS shall be met and the allowable shear values set forth in CBC Tables 2306.3(1), 2306.3(2) or 2306.3(3) shall only be permitted for structures assigned to Seismic Design Category A, B or C.
EXCEPTION: Where panels are fastened to framing members with staples, allowable shear values may be used if such values are substantiated by cyclic testing and approved by the Superintendent of Building.
The allowable shear values in CBC Tables 2306.3(1) and 2306.3(2) are permitted to be increased 40% for wind design. Panels complying with ANSI/APA PRP-210 shall be permitted to use design values for Plywood Siding in the AWC SDPWS.
91.2306.4. Shear Walls Sheathed with Other Materials. Sheer walls sheathed with Portland cement plaster, gypsum lath, gypsum sheathing or gypsum board shall be designed and constructed in accordance with AWC SDPWS. Shear walls sheathed with these materials are permitted to resist horizontal forces using the allowable shear capacities set forth in CBC Table 2306.3(3). Shear walls sheathed with Portland cement plaster, gypsum lath, gypsum sheathing or gypsum board shall not be used to resist seismic forces in structures assigned to Seismic Design Category E or F. (Amended by Ord. No. 186,488, Eff. 12/27/19.)
Shear walls sheathed with lath, plaster or gypsum board shall not be used below the top level in a multi-level building for structures assigned to Seismic Design Category D.
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