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Effects of long duration ground motions on the probability of drift exceedance for reinforced concrete frames near the Cascadia Subduction Zone Chin, David Holl Ling

Abstract

There are discrepancies in responses when a structure is subjected to short and long duration ground motions. The probability of drift exceedance has been repeated reported to increase under the influence of long duration records. Although the 2015 National Building Code of Canada has probabilistically taken the Cascadia Subduction Zone seismic hazards into considerations, none is known as what might happen to structures designed using this new Code if subjected to a large magnitude subduction earthquake. The answer is found via computer simulation. Following the general approach adopted in the Seismic Retrofit Guidelines 2nd Edition, incremental dynamic analysis is conducted to investigate discrepancies in the probability of drift exceedance for certain building types under both crustal and subduction ground motion records. These ground motions are selected and scaled to match the 2015 uniform hazard spectrum of Victoria, B.C. A simple shear wall model is first examined to generalize the effects of long duration ground motions. Then a similar study on a reinforced concrete frame is conducted to confirm these generalizations. Long duration ground motions seem to cause a higher probability of drift exceedance in moderately ductile buildings. However, no effect is observed in non-ductile and highly ductile buildings. The system internal capability to dissipate seismic energy by means of hysteretic loops is also contributing to the overall probability of drift exceedance. Its effect is more evident in the long duration as there are more load reversal cycles. Results discussion is provided, and potential ways to account for long duration in structural design are recommended.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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