Seismic screening of buildings based on the 2010 National Building Code of Canada

Seismic screening software is developed for existing buildings in Canada on the basis of the requirements of 2010 National Building Code of Canada. The software is based on the “Manual for Screening of Buildings for Seismic Investigation,” published by the National Research Council of Canada in 1992. The new software incorporates updated seismicity and soil classifications used in the National Building Code of Canada (NBCC) since 2005, as well as the new ductility and over-strength factors specified in the 2010 NBCC. The uniform hazard spectrum values of the current Canadian seismicity, defined for each municipality in Canada with a 2500 year earthquake return period, are used as reference hazard values. Seismic risk associated with the use of older seismic hazard values specified in older editions of the NBCC is identified relative to the current reference seismicity. The new site classifications are incorporated, while establishing relative soil amplification values between the new acceleration-based and velocity-based soil amplification factors and the foundation factors used in older codes. The new ductility and over-strength factors used in recent editions of the code are introduced in identifying different structural types with different toughness and energy dissipation capacities. The software can be used to conduct seismic screening of buildings located in different municipalities in Canada relative to the seismic requirements of NBCC-2010. It can also be used to generate tables for different locations in the country for manual screening of buildings.

Probabilistic Seismic Hazard Mapping of the Mississippi Embayment

Seismic hazard is calculated for a grid of sites on the Mississippi embayment and adjacent areas. The seismic zonations, seismicity parameters, and maximum magnitudes for these calculations were synthesized from the EPRI (Electric Power Research Institute) and LLNL (Lawrence Livermore National Laboratory) interpretations, augmented by information from recent relevant studies. Attenuation functions developed for this study include the effects of source size and crustal structure. The soil amplification factors include the effects of surficial geology, soil-column thickness, and soil nonlinearity. Seismic hazard maps, including the effect of site conditions, are presented for spectral accelerations at 1 and 10 Hz and for peak acceleration, for average return periods of 100, 500, and 1000 years. These maps show significantly lower ground-motion amplitudes than those reported by Algermissen et al. (1991). Because of these large differences, it is suggested that code- development decisions be made after consideration of both studies.