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TitleExploring risk-targeted ground motions for the national building code of Canada
AuthorAllen, T I; Luco, N; Halchuk, S
SourceProceedings of the 11th Canadian Conference on Earthquake Engineering; Earthquake Engineering and Engineering Vibration 2015, 9 pages
Alt SeriesEarth Sciences Sector, Contribution Series 20150102
PublisherCanadian Association for Earthquake Engineering
Meeting11th Canadian Conference on Earthquake Engineering; Victoria; CA; July 21-24, 2015
File formatpdf
ProvinceBritish Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut; Canada
NTS1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65; 66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560
Lat/Long WENS-141.0000 -50.0000 90.0000 41.7500
Subjectsengineering geology; geophysics; seismic risk; seismic zones; seismicity; earthquake damage; earthquakes; earthquake resistant design; earthquake risk
Illustrationsequations; graphs; earthquake maps
ProgramPublic Safety Geoscience Western Canada Geohazards Project
Released2015 01 01
AbstractSince 2012, the International Building Code (IBC) developed in the United States (US) has specified so-called Risk-Targeted Maximum Considered Earthquake (MCER) ground motions for designing new buildings and other structures. The MCER ground motions were developed by the Building Seismic Safety Council (with funding from the Federal Emergency Management Agency; FEMA) and the USGS for the 2009 NEHRP Recommended Seismic Provisions for New Buildings and Other Structures. In contrast to the uniform-hazard (for the most part) Maximum Considered Earthquake (MCE) ground motions specified in previous editions of the IBC, the MCER ground motions make use of all the probability levels on the underlying hazard curves that result from Probabilistic Seismic Hazard Analysis (PSHA). The MCE ground motions only considered values corresponding to a 2% probability of exceedance in 50 years, and in doing so, did not consider geographic differences in the ground motions at other probability levels (i.e., shapes of hazard curves). Perhaps more importantly, the MCE ground motions did not explicitly consider the risk of collapse of a building designed for such ground motions. Instead, they assumed that designing buildings against ground motions that have a uniform (2%-in-50-years) probability of being exceeded results in uniform collapse risk. As has since been shown for the US and other countries, however, the aforementioned geographic differences in shapes of hazard curves can result in inequitable risks of collapse. The MCER ground motions are calculated such that they result in a targeted level of collapse risk, and can be larger or smaller than corresponding uniform-hazard MCE ground motions.
Like pre-2012 editions of the IBC, the National Building Code of Canada (NBCC) specifies uniform-hazard ground motions with 2% probability of being exceeded in 50 years. This paper explores risk-targeted ground motions for Canada, using hazard curves proposed for the seismic provisions for the 2015 NBCC.
Summary(Plain Language Summary, not published)
Seismic design codes traditionally rely on maps that provide a "constant hazard" assumption where the Maximum Considered Earthquake (MCE) ground motions (or accelerations) used for building design are those that assume a uniform exceedance probability (e.g., 2% probability of exceedance in 50 years) that is constant across a spatial region. However, it has been suggested that it would be more consistent with the final use of seismic design maps to adopt a "constant risk" assumption in which the design ground motions are defined to provide to a certain level of risk (e.g., annual probability of collapse). The so-called Risk-Targeted Maximum Considered Earthquake (MCER) ground motions for designing new buildings lead to a nominal probability of collapse, or a uniform level of risk, over the time period and region of concern. The utility of risk-targeting for future editions of the National Building Code of Canada is discussed.

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