Seismic analysis method for steel frame structures considering fracture of structural members based on shaking table tests

Abstract

This paper proposes a seismic analysis method based on nonlinear dynamic analysis to consider the fracture of steel frame structural members during earthquakes. The approach corresponds to real fracture mechanism, especially low cycle fatigue failure. The fracture judgment condition in the analysis method was determined using the shaking table test for steel frame structures. In the shaking table tests, fractures at the column-beam connection which were considered to be due to fatigue cracks, were observed. From a fractographic study of the fracture surface and the Finite Element Analysis study after the test, these fractures were confirmed to be a result of low cycle fatigue; therefore, a low cycle fatigue evaluation method was integrated into the proposed analysis method. By applying both the proposed analysis method and the ordinal method which does not consider member fracture, the effects of member fracture on the seismic performance of a whole structure were examined. The effects on factors such as whole stiffness, equivalent periods and damage distributions after severe ground motion were marked. It is preferable that these effects be taken into account in seismic performance evaluations for very severe ground motions in which the occurrence of structural component failure is suspected.