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SANTA CLARA COUNTY CODE OF ORDINANCES: Sec. C3-36. Method of analysis.

Copyrighted by SANTA CLARA COUNTY CODE & Municipal Code Corporation, 1998.

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Sec. C3-36. Method of analysis.

(a) General: Every building within the scope of this chapter shall be analyzed and constructed to resist minimum total lateral seismic forces assumed to act nonconcurrently in the direction of each of the main axes of the building in accordance with the following equation:

V = ZIKCSW

The value of IKCS need not exceed the values set forth in Table D [Section C3-39], based on the applicable rating classification of the building.

(b) Lateral forces on elements of structures: Parts or portions of buildings shall be analyzed and designed for lateral loads in accordance with the applicable provisions of this chapter and Section 2312(e) of the UBC, but not less than the value from the following equation:

Fp = ZICp SWp

For the provisions of this subsection, the product of IS need not exceed the values as set forth in Table E [Section C3-39], but unreinforced masonry walls in buildings not having a rating classification of I may be analyzed in accordance with Section C3-37.

The value of Cp need not exceed the values set forth in Table F [Section C3-39].

(c) Anchorage and interconnection: Anchorage and interconnection of all parts, portions and elements of the building shall be analyzed and designed for lateral forces in accordance with Table F of this chapter and the equation Fp = ZICpSWp, as modified by Table E. Minimum anchorage of masonry walls to each floor or roof shall resist a minimum force of 200 pounds per linear foot acting normal to the wall at the level of the floor or roof.

(d) Level of required repair. Alterations and repairs required to meet the provisions of this chapter shall comply with all other applicable requirements of the Uniform Building Code unless otherwise specifically provided for in this chapter.

(e) Required analysis: Except as modified herein, the analysis and design relating to the structural alteration of existing buildings within the scope of this chapter shall be in accordance with the analysis specified in Chapter 23 of the UBC. A complete, continuous stress path from every part or portion of the building to the ground shall be provided for the required horizontal forces. All parts, portions or elements of the building shall be interconnected by positive means.

(f) Analysis procedure: Stresses in materials and existing construction utilized to transfer seismic forces from the ground to parts or portions of the building shall conform to those permitted by the Uniform Building Code and those materials and types of construction specified in Section C3-37. Materials and connectors used for interconnection of parts and portions of the building shall conform to the applicable provisions of the UBC. Nails may be used as part of an approved connector. Except as modified herein, unreinforced masonry walls shall be analyzed as specified in Sections 2406, 2407 and 2408 of the UBC to withstand all vertical loads as specified in Chapter 23 of the UBC, in addition to the seismic forces required by this chapter. The 50 percent increase in the seismic force factor for shear walls as specified in Section 2407(h)4F of the UBC may be omitted in the computation of seismic loads to existing shear walls. No allowable tension stress shall be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this chapter shall be strengthened or shall be removed and replaced. It is understood, however, that unreinforced masonry walls in buildings not classified as a rating classification I in Table A [Section C3-39] may be analyzed in accordance with Section C3-37, and that an unreinforced masonry wall which carries no design loads other than its own weight may be considered as veneer if it is adequately anchored to new supporting elements.

(g) Combination of vertical and seismic forces:

(1) New materials: All new materials introduced into the building to meet the requirements of this section which are subjected to combined vertical and horizontal forces shall comply with Section 2303(f) of the UBC.

(2) Existing materials: When stresses in existing lateral force resisting elements are due to a combination of dead loads plus live loads plus seismic loads, the allowable working stress specified in the UBC may be increased 100 percent. However, no increase will be permitted in the stresses allowed in Section C3-37, and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by Section 2303(d) of the UBC.

(3) Allowable reduction of bending stress by vertical load: In calculating tensile fiber stress due to seismic forces required by this chapter, the maximum tensile fiber stress may be reduced by the full direct stress due to vertical dead loads.

(Ord. No. NS-1100.78, § VII, 12-12-89; Ord. No. NS-1100.88, § 2, 6-29-99)