Seismic risk decision framework for existing buildings in Canada
Preliminary Seismic Risk Screening Tool
A preliminary seismic risk screening tool was developed 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 were evaluated against the next level of seismic risk screening tool to ensure consistency. A flowchart was developed to facilitate adoption of the new tool by practicing engineers and other end-users.
Semi-quantitative Seismic Risk Screening Tool
The National Research Council Canada recently developed a Semi-Quantitative Seismic Risk Screening Tool (SQST) for seismic risk screening of existing buildings in Canada. This paper presents the structural seismic risk scoring methodology that is part of the SQST. The basic methodology is based on the FEMA P-154 methodology but has been heavily modified to suit Canadian seismicity and seismic design and construction practices. Buildings are assessed and evaluation based on a semi-quantitative structural scoring system that incorporates elements of construction, seismicity, condition, and other key parameters. Structural scores are obtained by adding structural basic scores and applicable score modifiers. For an existing building, a structural basic score is determined by calculating the probability of collapse on the basis of a number of assumptions. Then a series of score modifiers are calculated to address the effects of applicable building characteristics on the building’s seismic performance. The structural score is compared with an acceptable structural threshold to determine whether the structural seismic risk is acceptable. The objective of the proposed methodology is to ensure an acceptable and consistent seismic risk in building portfolios while minimizing life safety threats.