Investigation of strong-motion duration consistency in endurance time excitation functions

The endurance time (et) method is a dynamic analysis procedure usingintensifying excitation. the et excitation functions are generated so that structuralperformance can be assessed at dierent excitation levels in a single response historyanalysis. et accelerograms, which have been generated so far, possess response spectraconsistency; this means that the duration consistency has not been directly considered.strong-motion duration can inuence the response of structures which have stinessor strength degrading characteristics. in this paper, several well-known strong-motionduration denitions are studied in the context of the et method. ground motions arescaled to spectral acceleration of the code spectrum as well as the et records; furthermore,the et records are scaled to have consistent duration compared to real ground motion,considering dierent strong-motion duration denitions. in order to determine whichdenitions have the highest correlation with structure responses, several sdof structuresthat have cyclic deteriorating behavior in stiness and strength are subjected to bothet records and real ground motions. since maximum inter story drift and maximumdisplacement of a structure subjected to several motions with roughly the same accelerationspectra but dierent motion durations are approximately identical, in this paper, the aimis to pursue the inuence of motion duration in responses. those indices which are basedon energy and accumulative damage are employed. correlation of each denition withstructure responses has been examined by comparing the results of the et records and realground motion. good performance of the et records in a nonlinear region can be deduceddue to the high correlation between the results of et records and real ground motion. thispaper provides an approach for considering the duration consistency in et accelerograms.the eciency of this approach for current et accelerograms is also investigated.