Ord 2002-018 - Laserfiche WebLink

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(3) Unreinforced Masonry Walls. Except as modified herein, unreinforced masonry walls shall be analyzed as specified in Section 2406, 2407 and 2408 to withstand all vertical loads as specified in Chapter 23 of the Uniform Building Code in addition to the seismic forces required by this Article. The 50 percent increase in the seismic force factor for shear walls as specified in Section 2407(h)4F of the Uniform Building Code maybe omitted in the computation of seismic loads to existing shear walls. No allowable tension stress will be permitted in unreinforced masonry walls, except as specified in Section 7-5-860. Walls not capable of resisting the required design forces specified in this Article shall be strengthened or shall be removed and replaced. (4) Unreinforced Masonry Infill Walls. Unreinforced masonry infill walls shall be analyzed for both in-plane and out-of--plane seismic forces per Section 7-5-865. Infill walls not capable of resisting the required design forces shall be strengthened or shall be removed and replaced. If infill walls are removed, the space frame shall be capable of resisting 3/4 of the required design loads per Section 7-5-1150A(a) alone, or shall be strengthened. EXCEPTION: Frame and Masonry Infill in Combination. If the stiffness of the frame alone under 2.25 times the required design loads (per Section 7-5-855) results in a deflection of no more than 1/360 times the story height, infill walls maybe designed to resist out-of--plane loads only. The strength of the space frame shall be sufficient to resist 3/4 of the required design loads per Section 7-5-855). The frame maybe strengthened and stiffened by bracing to achieve these requirements. (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). (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 Uniform Building Code maybe increased 100 percent. However, no increase will be permitted in the stresses allowed in Section 7-5-860, and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by Section 2303(d) of the Uniform Building Code. (3) Allowable Reduction of Bending Stress by Vertical Load. In calculating tensile fiber stress due to seismic forces required by this Article, the 7