Site classification methodology for TS 1170.5 design spectra

• DOI: 10.5459/bnzsee.1686
• Publication Date: 2025-03-01T06:00:13Z
• Authors: Robin Lee; Misko Cubrinovski; Brendon Bradley

The Technical Specification (TS) 1170.5 has been developed to incorporate the output of 2022 New Zealand National Seismic Hazard Model revision (NSHM2022) [1] and update Clause B1 Verification Method 1 (B1/VM1) Building Code. In this paper, we discuss proposed site classification methodology based on Vs(30) (i.e., time-averaged shear-wave velocity from ground surface 30 m depth) which is used effects in TS design spectra. reasoning for use classification, a significant departure Standards NZS [2], first elaborated. Based detailed scrutiny uniform hazard spectra obtained NSHM2022, seven classes are proposed, with associated six classes. Multiple objectives were considered definition classes, principal goal being represent relevant conditions robust yet practical manner, appropriate engineering practice. As parameter scheme, establishment Vs profile at critical step. Several methods obtaining profile, measured or inferred, subsequent calculation recommended. Each method different uncertainty factor that affects both consequent context, multiple class must be adopted an envelope spectrum cases where range values span several Importantly, variation due relatively small compared themselves (due uncertainties NSHM2022 PSHA). For sites not well-represented within PSHA performed site-specific (special) studies