Ground motion input for NLRHA: practical limitations of NZS 1170.5 and comparison to US standards
Nonlinear response history analysis (NLRHA), or so-called “nonlinear time history analysis”, is adopted by practicing structural engineers who implement performance-based seismic design and/or assessment procedures. One important aspect in obtaining reliable output from the NLRHA procedure is the input ground motion records. The underlying intention of ground motion selection and amplitude-scaling procedures is to ensure the input for NLRHA is representative of the ground shaking hazard level, for a given site and structure. This paper provides a summary of the salient limitations of the ground motion selection and scaling requirements in Sections 5.5 and 6.4 of the New Zealand (NZ) loading standard NZS 1170.5 (2004). Also discussed within, there are implications for more modern guidance documents in NZ, such as the draft and the 2017 “Assessment Guidelines” for existing buildings, which cite NZS 1170.5. To emphasize the above issues with NZS 1170.5, this paper presents a summary of contemporary approaches in the US standards ASCE 7-16 (new buildings) and ASCE 41-17 (existing buildings). This paper presents a truncated version of an article submitted for publication in the New Zealand Society for Earthquake Engineering Bulletin. The reader is encouraged to refer to the journal paper for more detailed discussion, including other subjects (not discussed within, for brevity).