Comparison of Seismic Screening Methods for Schools in a Moderate Seismic Zone

Abstract eng:
An ongoing project at McGill University is aimed at designing an adapted seismic screening method for schools in the province of Québec, Canada. As part of this project the “FEMA154 Rapid Visual Screening of Buildings for Potential Seismic Hazard” and the “NRC92 Manual for Screening of Buildings for Seismic Investigation” were used to assess the potential performance of 100 school buildings located in the city of Montréal. Results for both methods are in reasonable agreement, with 65% of the buildings requiring a detailed evaluation according to FEMA154 and 50% according to NRC92. The evaluation highlighted particular characteristics of the structures. School buildings are generally low-rise, of a limited number of structural types and have a high incidence of features that could affect seismic performance, such as steps in elevation and re-entrant corners. Findings were also used to identify advantages and shortcomings of each screening method. NRC92 is largely based on expert opinion, which makes the method difficult to update. FEMA154 uses a more rational methodology for calculating the vulnerability scores; however the nonlinear static seismic analysis procedure employed doesn’t consider latest improvements in building codes. Updating the procedure increases the basic scores on average by 24%, with higher scores indicative of better performance. When using FEMA154 it has to be considered that seismicity and soil amplification factors were developed for the United States. NRC92, although conceived for the Canadian context, has to be updated to include latest findings in seismic hazard parameters and soil classification. Since schools typically have a high incidence of irregularities, accounting for them in the screening phase is essential. FEMA154 only considers vertical and plan irregularities and it was found that this is insufficient to capture the characteristics of the evaluated schools. NRC92 partially overcomes this shortcoming by specifying seven different types of irregularities. In conclusion it was recognized that the clear analytical procedure behind FEMA154 allows updating and adapting the method to its use outside its intended scope. Therefore the screening procedure currently under development is largely based on this method, incorporating key characteristics of NRC92.

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