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Earthquakes and Structures
  Volume 14, Number 6, June 2018, pages 577-587

Average spectral acceleration: Ground motion duration evaluation
Jack Banahene Osei and Mark Adom-Asamoah

Abstract     [Full Text]
    The quantitative assessment of the seismic collapse risk of a structure requires the usage of an optimal intensity measure (IM) which can adequately characterise the severity of the ground motion. Research suggests that the average spectral acceleration (Saavg) may be an efficient and sufficient alternate IM as compared to the more traditional first mode spectral acceleration, Sa(T1), particularly during seismic collapse risk estimation. This study primarily presents a comparative evaluation of the sufficiency of the average spectral acceleration with respect to ground motion duration, and secondarily assesses the impact of ground motion duration on collapse risk estimation. By assembling a suite of 100 historical ground motions, incremental dynamic analysis of 60 different inelastic single-degree-of-freedom (SDF) oscillators with varying periods and ductility capacities were analysed, and collapse risk estimates obtained. Linear regression models are used to comparatively quantify the sufficiency of Saavg and Sa(T1) using four significant duration metrics. Results suggests that an improved sufficiency may exist for Saavg when the period of the SDF system increases, particularly beyond 0.5, as compare to Sa(T1). In reference to the ground motion duration measures, results indicated that the sufficiency of Saavg is more sensitive to significant duration definitions that consider almost the full wave train of an accelerogram (SDa5-95 and SDv5-95). In order to obtain a reduced variability of the collapse risk estimate, the 5-95% significant duration metric defined using the Arias integral (SDa5-95) should be used for seismic collapse risk estimation in conjunction with Saavg.
Key Words
    average spectral acceleration; sufficiency; significant duration; earthquake-induce ground motion
Jack Banahene Osei and Mark Adom-Asamoah: Department of Civil Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

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