(A) General.
(1) Every structure within the scope of this subchapter 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 structure in accordance with the following equation:
V = IKCSW. . . . . . . . .(15-1)
(2) The value of IKCS need not exceed the values set forth in § 4 of the appendix following this chapter based on the applicable rating classification of the building.
(B) Lateral forces on elements of structures.
(1) Parts or portions of structures shall be analyzed and designed for lateral loads in accordance with division (A) of this section and the Uniform Building Code, Chapter 23, § 212, but not less than the value from the following equation:
Fp = ICpSWp. . . . . . . . .(15-2)
(2) For the provisions of this division, the product of IS need not exceed the values as set forth in § 5 of the appendix following this chapter.
(3) Exception. Unreinforced masonry walls in buildings not having a rating classification of I may be analyzed in accordance with § 150.088 of this subchapter.
(4) The value of Cp need not exceed the values set forth in § 6 of the appendix following this chapter.
(C) Anchorage and interconnection. Anchorage and interconnection of all parts, portions and elements of the structure shall be analyzed and designed for lateral forces in accordance with § 6 of the appendix following this chapter and the equation Fp = ICpSWp as modified by § 6 of the appendix following this chapter 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 subchapter shall comply with all other applicable requirements of this code unless specifically provided for in this subchapter.
(E) Required analysis.
(1) General. Except as modified herein, the analysis and design relating to the structural alteration of existing structures within the scope of this subchapter shall be in accordance with the analysis specified in the Uniform Building Code, Chapter 23.
(2) Continuous stress path. A complete, continuous stress path from every part or portion of the structure to the ground shall be provided for the required horizontal forces.
(3) Positive connections. All parts, portions or elements of the structure shall be interconnected by positive means.
(F) Analysis procedure.
(1) General. Stresses in materials and existing construction utilized to transfer seismic forces from the ground to parts or portions of the structures shall conform to those permitted by the code and those materials and types of construction specified in § 150.088 of this subchapter.
(2) Connections. Materials and connectors used for interconnection of parts and portions of the structure shall conform to the code. Nails may be used as part of an approved connector.
(3) Unreinforced masonry walls.
(a) Except as modified herein, unreinforced masonry walls shall be analyzed as specified in the Uniform Building Code, Chapter 24, §§ 2808 and 2809, to withstand all vertical loads, as specified in Chapter 23 of the Uniform Building Code, in addition to the seismic forces required by this subchapter. The 50% increase in the seismic force factor for shear walls as specified in § 8 of the appendix following this chapter may be omitted in the computation of seismic loads to existing shear walls.
(b) No allowable tension stress will be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this subchapter shall be strengthened or removed and replaced.
(c) Exceptions.
1. Unreinforced masonry walls in buildings not classified as a rating classification I pursuant to § 1 of the appendix following this chapter may be analyzed in accordance with § 150.088 following this chapter.
2. Unreinforced masonry walls which carry no design loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements.
(G) Combination of vertical and seismic forces.
(1) New materials. All new materials introduced into the structure to meet the requirements of this section which are subjected to combined vertical and horizontal forces shall comply with the Uniform Building Code, Chapter 23, § 2312.
(2) Existing materials. When stresses in existing lateral force-resisting elements are due to a combination of dead loads plus seismic loads, the allowable working stress specified in the code may be increased 100%. However, no increase will be permitted in the stresses allowed in § 150.088 of this subchapter, and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by the Uniform Building Code, Chapter 23.
(3) Allowable reduction of bending stress by vertical load. In calculating tensile fiber stress due to seismic forces required by this subchapter, the maximum tensile fiber stress may be reduced by the full direct stress due to vertical dead loads.
('65 Code, § 8-15.08) (Ord. 321-C.S., passed - - ) Penalty, see § 10.99