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Earthquakes and Structures
  Volume 8, Number 2, February 2015 , pages 443-462

Evaluating the reliability of using the deflection amplification factor to estimate design displacements with accidental torsion effects
Jui-Liang Lin, Wei-Chun Wang and Keh-Chyuan Tsai

    Some model building codes stipulate that the design displacement of a building can be computed using the elastic static analysis results multiplied by the deflection amplification factor, Cd. This approach for estimating the design displacement is essential and appealing in structural engineering practice when nonlinear response history analysis (NRHA) is not required. Furthermore, building codes stipulate the consideration of accidental torsion effects using accidental eccentricity, whether the buildings are symmetric-plan, or asymmetric-plan. In some model building codes, the accidental eccentricity is further amplified by the torsional amplification factor Ax in order to minimize the discrepancy between statically and dynamically estimated responses. Therefore, this warrants exploration of the reliability of statically estimated design displacements in accordance with the building code requirements. This study uses the discrepancy curves as a way of assessing the reliability of the design displacement estimates resulting from the factors Cd and Ax. The discrepancy curves show the exceedance probabilities of the differences between the statically estimated design displacements and NRHA results. The discrepancy curves of 3-story, 9-story, and 20-story example buildings are investigated in this study. The example buildings are steel special moment frames with frequency ratios equal to 0.7, 1.0, 1.3, and 1.6, as well as existing eccentricity ratios ranging from 0% to 30%.
Key Words
    reliability; deflection amplification factor; accidental torsion effect; torsional amplification factor; seismic responses; nonlinear response history analysis
Jui-Liang Lin: National Center for Research on Earthquake Engineering, Taiwan

Wei-Chun Wang and Keh-Chyuan Tsai: Department of Civil Engineering, National Taiwan University, Taiwan

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