FEMA P-695 Verification of Seismic Design Coefficients for Mid-to-High-Rise Hybrid Coupled Core Wall Systems

Abstract

FEMA P-695 is a framework that allows verification of the appropriateness of the seismic design coefficients (namely, the overstrength factor, the seismic reduction factor, and the displacement amplification factor) by means of a statistical approach that ultimately provides a pass/fail evaluation of the coefficients for the building prototypes considered. The study presented in this paper focuses on coupled core wall systems using steel coupling beams, with the goal of demonstrating that these systems can be designed using less conservative coefficients than those currently prescribed. A secondary goal of this study is to demonstrate that these systems can also be designed for heights in excess of the current limitations provided in the ASCE 7-16 standard. The study presented consists of a large number of archetype structures, differing by height, floor plate dimensions, amount of vertical forces applied, and fundamental frequencies. Each of the archetype structures is subject to a suite of 22 near-field acceleration records, and for each record an incremental dynamic analysis is performed. The results of thousands of nonlinear dynamic analyses are summarized in this paper, showing that hybrid coupled core wall systems can be safely designed using the largest seismic reduction coefficient currently allowed (R = 8), without a correspondingly unduly large overstrength factor and displacement amplification factor. The paper provides some information on the design approach for these systems, as well as a summary of all analyses performed, highlighting which of the archetypes are less likely to perform well under the conditions investigated. In conclusion, the paper shows that a FEMA P-695 verification of coupled core wall system supports the use of a higher seismic reduction factor for buildings in excess of the height limitation currently in ASCE 7-16.