§ 8-11.04. Local amendments.

The provisions of this Chapter shall constitute local amendments to the cross-referenced provisions of the California Building Code and shall be deemed to replace the cross-referenced section of the California Building Code with the respective provisions set forth in this Chapter.

SECTION 1613 SEISMIC DESIGN REQUIREMENTS.

The following section is hereby added to the Code:

1613.5.2 Modify ASCE 7 12.11.2.2.3. 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 toe 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 wood diaphragms supporting concrete or masonry walls, wood diaphragms shall comply with the following:

1. 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.

2. The maximum diaphragm shear used to determine the depth of the subdiaphragm shall not exceed 75% of the maximum diaphragm shear.

FINDINGS:

Local Geological Conditions - The City of Simi Valley, greater Ventura County area, and southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. This amendment is required to address and clarify special needs of horizontal wood diaphragms transferring seismic forces from concrete or masonry walls. This modification requires seismic compatibility of walls with the diaphragm, and needs to be incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

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SECTION 1809.7 FOUNDATIONS.

This section is hereby amended to read as follows:

2. When buildings are located on expansive soil having an expansion index greater than 50, gutters, downspouts, piping, and/or other non-erosive devices shall be provided to collect and convey rainwater to a street, storm drain, or other approved watercourses or disposal area.

Foundations in expansive soil shall be designed to comply with the following Table:

Number of Floors Supported by Foundation	Thickness of Foundation Wall (Inches)		Width of Footing (Inches)	Thickness of Footing (Inches)	Depth of Footing (Inches)
	Concrete	Masonry
1	6	6	12	6	24
2	8	8	16	8	24

 

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FINDINGS:

Local Geological, Topographic Conditions - The City of Simi Valley, the greater Ventura County area, and the southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. The City contains areas designated as flood zones, liquefaction, and landslide hazards. These amendments are required to address and clarify special needs to reduce hazards resulting from liquefaction or soil displacement due to strong seismic events. This modification to improve design and construction methods for foundations of structures shall be incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

2305.4 Hold-down connectors. Hold-down connectors shall be designed to resist shear wall overturning moments using approved cyclic load values or 75 percent of the allowable earthquake load values that do not consider cyclic loading of the product. Minimum connector bolt diameter shall be ½ inch. Connector bolts into wood framing 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-downs shall be re-tightened just prior to covering the wall framing.

FINDINGS:

Local Geological Conditions — The City of Simi Valley, greater Ventura County area, and southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. The modification to establish certain performance requirements for hold-down connectors, which is essential to preventing failure of a shear wall due to excessive deflection, shall be incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

2305.5 Quality of Nails. 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. No clipped head or box nails 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.

FINDINGS:

Local Geological Conditions — The City of Simi Valley, greater Ventura County area, and southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. The modification to require mechanically driven nails to have the same dimension as hand driven nail resulting in improve quality of construction and performance of shear wall panels shall be incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

SECTION 2306 ALLOWABLE STRESS DESIGN.

This section is hereby amended to read as follows:

2306.4 Lumber sheathed shear walls. Single and double diagonally sheathed lumber shear walls shall be designed in accordance with AF&PA SDPWS. Single and double diagonally sheathed lumber walls shall not be used to resist seismic forces in structures assigned to Seismic Design Category D, E or F.

2306.4.1. Wood-framed shear walls. Wood-framed shear walls shall be designed and constructed in accordance with AF&PA SDPWS. Wood structural panel thickness for shear walls shall not be less than nominal 15/32 inch thick and studs shall not be spaced at more than 16 inches on center.

The maximum allowable shear value for three-ply plywood resisting seismic forces is 200 pounds per foot (2.92 kn/m). 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 (9.5 mm) from the edge of the connecting members for shear greater than 350 pounds per foot (5.11 kn/m). Nails shall be placed not less than 3/8 inch (9.5 mm) from panel edges and not less than 1/4 inch (6.4 mm) from the edge of the connecting members for shears of 350 pounds per foot (5.11 kn/m) or less.

Any wood structural panel sheathing used for diaphragms and shear walls that are part of the seismic-force-resisting system shall be applied directly to framing members.

Exception: Wood structural panel sheathing in a horizontal 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.

The wood-framed shear walls using staples as fasteners shall not be permitted.

Exception: Staples designated in Table 2306.3(1) of this Code may be used for wood structural panel shear wall to resist seismic loading, when the allowable shear values of Table 2306.3(1) of this Code, or greater, are substantiated by cyclic testing and approved by the Building Official.

2306.7 Shear walls sheathed with other materials. 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 D, E or F.

FINDINGS:

Local Geological Conditions - The City of Simi Valley, the greater Ventura County area, and southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. Gypsum wallboard and exterior Portland cement plaster have performed poorly during recent California seismic events. (Such as Loma Prieta and Northridge.) The shear values for gypsum wallboard and Portland cement stucco and staple fasteners contained in the Code are based on mono-directional testing only. The limitation on the use of these systems as set forth in the amendment until cyclic loading testing are performed and evaluated in a more rigorous standard which will better prevent damage to a structure's lateral load resisting system which can result from local conditions. This modification is incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

Section 2308 Conventional light-framed construction.

This section is here by amended to read as follows:

2308.3.4 Braced wall line support. Braced wall lines shall be supported by continuous foundations.

2308.6.3.1 Braced wall line sheathing. Wall panel method shall be WSP with a minimum thickness of 15/32 inch for seismic design category D and E.

2308.6.3.2 Attachment of sheathing. Fastening of braced wall panel sheathing shall not be less than that prescribed in Table 2304.10.1. Wall sheathing shall not be attached to framing members by adhesives.

All braced wall panels shall extend to the roof sheathing and shall be attached to parallel roof rafters or blocking above with framing clips (18 gauge minimum) spaced at maximum 24 inches (6,096 mm) on center with four 8d nails per leg (total eight 8d nails per clip). Braced wall panels shall be laterally braced at each top corner and at maximum 24 inch (6,096 mm) intervals along the top plate of discontinuous vertical framing.

TABLE 2308.12.4

WALL BRACING IN SEISMIC DESIGN CATEGORIES D AND E
(Minimum Length of Wall Bracing per each 25 Linear Feet of Braced Wall Line ^a )

CONDITION	SHEATHING TYPE b	S DS < 0.50	0.50 ≤S DS < 0.75	0.75 ≤ S D S ≤ 1.00	S DS > 1.00
One Story	S-W d	5 feet 4 inches	8 feet 0 inches	9 feet 4 inches	12 feet 0 inches

 

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

a. Minimum length of panel bracing of one face of the wall for S-W sheathing shall be at least 4'-0" long. For S-W panel bracing of the same material on two faces of the wall, the minimum length is permitted to be one-half the tabulated value but the h/w ratio shall not exceed 2:1 and design for uplift is required.

b. S-W = Wood structural panels.

d. S-W sheathing shall be 15/32″ thick nailed with 8d nails, at 6:6:12.

FINDINGS:

Local Geological Conditions — The City of Simi Valley, greater Ventura County area, and southern California region is a densely populated area having buildings constructed over and near a vast array of fault systems capable of producing major earthquakes, including but not limited to the 1994 Northridge Earthquake. Conventional framing does not address the need for a continuous load path, critical shear transfer mechanisms, connection ties, irregular and flexible portions of complex shaped structures. Unless designed by a registered design professional, such buildings built by conventional framing requirements will be prone to serious damage in future large earthquakes. This modification shall be incorporated into the Code to assure that new buildings and additions to existing buildings are designed and constructed in accordance with the scope and objectives of the California Building Code. For this reason, this jurisdiction determines that these amendments are reasonably necessary.

(§ 1 (Exh. A), Ord. No. 1262, eff. January 5, 2017)