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20.08.109 (24 CCR), and including by reference the Uniform Building Code, is amended to read as follows: 1630.4.2 Vertical combinations. The value of R used in the design of any story shall be less than or equal to the value of R used in the given di- rection for the story above. EXCEPTION: This requirement need not be applied to a story where the dead weight above that story is less than 10 percent of the total dead weight of the structure. Structures may be designed using the procedures of this section under the following conditions: 1. The entire structure is designed using the lowest R of the lateral- force-resisting systems used, or 2. The following two-stage static analysis procedures may be used for structures conforming to Section 1629.8.3, Item 4. 2.1 The flexible upper portion shall be designed as a separate structure, supported laterally by the rigid lower portion, using the appropriate values of R and p. 2.2 The rigid lower portion shall be designed as a separate structure using the appropriate values of R and p. The reactions from the upper portion shall be those determined from the analysis of the upper portion multi- plied by the ratio of the (R/p) of the upper portion over (R/p) of the lower portion. This ratio shall not be taken less than 1.0. (Ord. 1869 § 2, 2002) 20.08.110 Section 1630.7 - Amended -Horizontal Torsional Moments: Section 1630.7 of the California Building Standards Code 2001 Edition (24 CCR), and including by reference the Uniform Building Code, is amended to read as follows: 1630.7 Horizontal Torsional Mo- ments. Provisions shall be made for the increased shears resulting from horizontal torsion where diaphragms are not flexible. The most severe load combination for each element shall be considered for design. The torsional design moment at a given story shall be the moment resulting from eccentricities between applied design lateral forces at levels above that story and the vertical- resisting elements in that story plus an accidental torsion. The accidental torsional moment shall be determined by assuming the mass is displaced as required by Section 1630.6. Where torsional irregularity exists, as defined in Table 16-M, the effects shall be accounted for by increasing the accidental torsion at each level by an amplification factor, AX, deter- mined from the following formula: S max 1 z Ax = ~ 1.2Savg J (30-16) WHERE: Savg =the average of the story drift at the extreme points of the structure at Level x. 704-15 (Pleasanton April 2003)