Yu, Tingtingdel Rey Castillo, Enrique2025-04-112025-04-112024-01-01(2024) 20th fib Symposium, 2209-2219.2617-4820https://hdl.handle.net/2292/71879Precast concrete diaphragms play a critical role on the seismic performance of structures, and increasing attention is being paid to strengthen these structural elements in the aftermath of the 2010/2011 Canterbury earthquakes. However, a significant gap remains in our understanding of the seismic forces that diaphragm elements should be assessed or designed for. Various key parameters affecting the seismic demands of diaphragms such as higher mode effects, plan and vertical irregularities and the role of over-strength capacity of the lateral resisting elements are not comprehensively addressed in current design and assessment documents. These missing aspects have raised questions about the adequacy of the simplistic design methods commonly used in national documents. The New Zealand loading standard NZS 1170.5 specifies a pseudo-Equivalent Static Analysis (pESA) approach for calculating diaphragm forces, taking into account Peak Ground Acceleration (PGA) and structural overstrength. Conversely, the US loading standard ASCE 7-22 introduces an alternative method for precast concrete diaphragms, utilizing a diaphragm design force reduction factor, Rs, while also including considerations for higher mode effects and structural overstrength. These aspects often lead to higher force demands compared to the general method in ASCE 7-22, used for other diaphragm types, but the accuracy of these methods in estimating diaphragm demands remains an open question. This study aims to bridge this gap by conducting a comparative analysis of the NZS1170.5 and US approaches to determine seismic forces demand in the diaphragm. The various documents are brought to a comparable framework by aligning key seismic design parameters such as response spectra, ductility and overstrength. The diaphragm forces were calculated using both standards and on a representative New Zealand building archetype to assess the efficacy of each standard's approach. The findings of the study offer critical insights into the calculation of diaphragm forces under US and NZ standards. This research contributes significantly to the field by aiding engineers in making informed decisions regarding the seismic design and assessment of buildings, ultimately enhancing structural resilience in earthquake-prone areas.Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher.https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmConference ItemCopyright: FIB International