Development of a preliminary seismic risk screening tool for existing buildings in Canada

Abstract

This paper presents a preliminary seismic risk screening tool to identify buildings whose superior structural and non-structural seismic performance in regions of low seismicity can be assessed based on several key attributes. The tool is designed to exempt buildings from detailed seismic risk assessment if key exemption criteria are met. The exemption criteria are based on: a seismic categorization system linked to anticipated building damage and seismicity; whether or not the building was designed using modern seismic design provisions; and the remaining time that the building will be occupied. The tool also provides a second list of criteria, which if satisfied, will automatically trigger further detailed seismic risk assessment. The decisions rendered by the tool regarding the expected seismic performance of a building are evaluated against the next level of seismic risk screening tool to ensure the consistency. A flowchart is presented to facilitate adoption of the tool by practicing engineers and other end-users.

An update on the seismic categorization for seismic risk assessment of existing Canadian buildings

“…In 2018, NRC developed multi-level seismic risk screening tools (SRSTs) to assist building owners in efficiently assessing the seismic risk of existing Canadian buildings within their portfolios (Motazedian, 2017;Fathi-Fazl et al 2018;Fathi-Fazl et al 2020a;Fathi-Fazl et al 2020b;Fathi-Fazl et al 2020c;Fathi-Fazl et al 2020d;Fathi-Fazl et al 2021). The NRC SRSTs associated six seismic categories (very low, low, moderate, moderately high, high, and very high) with various MMI values.…”

“…Existing buildings in very low and low seismic categories are therefore eligible to be exempt from further seismic risk assessment as their 475-year return period shaking is considered too low to cause appreciable damage depending on the consequences of their failure (Fathi-Fazl and Lounis, 2017;Fathi-Fazl et al 2020e). The seismic categorization system in the NRC SRSTs (Fathi-Fazl et al 2018) 2007; Worden et al 2012;Caprio et al 2015;Halchuk, 2017). In addition, a set of PGV-S a relationships were determined by applying regression analysis to a seismic database of over 200,000 grid points provided by Halchuk et al (2015) for Natural Resources Canada (NRcan).…”

“…To maintain consistency with the NBC 2015 and to the benefit of practising engineers, the S a thresholds in Table 1 (Fathi-Fazl et al 2018) were adjusted to be consistent with the thresholds of spectral response accelerations during the short periods provided in Table 4.1.8.9 in Part 4 of the NBC 2015. It is noted that the NBC 2015 provided only a single threshold of 0.3 g for spectral response accelerations over long periods.…”

“…Site coefficients were incorporated into the thresholds for defining seismic categories (see Table 2) to address soil conditions. Figure 1 presents an earthquake hazard map based on seismic categories assuming site class C following thresholds values given in Table 1 (Fathi-Fazl et al 2018). Adams et al (2020) provided new design PGA and S a (T) values at 0.2, 0.5, 1.0, 2.0, 5.0, and 10.0 seconds for existing Canadian buildings abroad.…”

Seismic Analysis of Unreinforced Masonry Structures with Plan Irregularities

“…The screening tool is a high-level evaluation tool for assessing the generalized need for seismic upgrades to the subject building, based on the following parameters of the subject building and its geographic location: seismicity, benchmark NBC edition, remaining occupancy time, and consequences of failure. (Fathi-Fazl et al, 2020) The Level 1 PST Screening Form is shown in Figure 31. The NRC's seismic risk framework also consists of a second and third level of risk management: Semi-Quantitative Seismic Risk Screening Tool (SQST), and Seismic Evaluation Guidelines.…”