Effect of Ground Motion Duration on Seismic Design Load for Civil Engineering Structures : Development of Equivalent Ground Acceleration (EQA)

Abstract

The effect of ground motion duration on seismic loads for structural design is studied in terms of the equivalent ground acceleration (EQA). EQA is obtained by multiplying the peak ground acceleration (PGA) by a reduction factor (EQA factor), which takes into account the peak response ratio relative to its standard values and the effective level of response affecting structural failure. Both are evaluated in connection with the duration of the input ground motion. EQA is considered to be a direct measure of destructiveness of earthquake ground motion, and will provide straightforward information for determining and interpreting the design seismic load. An EQA model is proposed and formulated. On this basis, the effect of a strong motion duration on the seismic design load is discussed, using numerical results for recorded accelerograms. Statistical models are developed so that EQA can be estimated on a hand-caluculator basis.