301 N Broadway - Shell & Core - Plan

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3rd & Broadway, Santa Ana, CA Volume 2 - Structural Calculations June 17, 2024 | Project # S21043.00 pg. 54 4.4.3 ASCE 7-16 BUILDING HEIGHT INCREASE ALLOWANCE CHECK According to ASCE 7-16 Section 12.2.5.4, the limits on structural height in Table 12.2-1 are permitted to be increased from 160ft to 240 ft for structures assigned to Seismic Design Categories D with special reinforced concrete cast-in-place shear walls if both of the following requirements are met: 1. The structural shall not have an extreme torsional irregularity as defined in Table 12.3-1. As shown in section 4.4.2, the Residential Building does not have extreme torsional irregularity in either X or Y direction, therefore the provision is satisfied. The Hotel Building height is less than 160ft, therefore the provision does not apply. 2. The special reinforced cast-in-place concrete shear walls in any one plane shall resist not more than 60% of the total seismic forces in each direction, neglecting accidental torsional effects. While a few levels of the structure demonstrate shear distribution along gridline “RH” are slightly greater than 60% of the total lateral load under an x-direction response spectrum case, TT does not believe that the orientation of the lateral resisting system in the residential building is a configuration that is anticipated to be governed by this provision. Primarily as the two concrete cores are separated by roughly 100ft of a continuous diaphragm, and that cores provide a significant amount of redundancy. It is unlikely that a shear failure of one wall would lead to failure of the other wall along this line as the diaphragm will be able to redistribute forces among the remaining 3 walls of the core due in part because of the torsional resistance of the separated cores. The lateral framing condition at the residential building (double cores) is not a common enough condition to be properly addressed by a standard code provision. It is further noted that the commentary for this section (C12.2.5.4) notes that the second requirement, regarding percent of load to each wall line, is similar to a redundancy requirement and meant to prohibit a system that is overly dependent on a single line of framing or walls. As noted above, the inherent stability of the cores and the continuous diaphragm make the system redundant, allowing load to be redistributed if necessary. The Hotel Building height is less than 160ft, therefore the provision does not apply.