THE CALCULATION OF SEISMIC FORCE WITH DIFFERENT DUCTILITY FACTOR IN STRENGTH DEGRADING SYSTEM

Abstract:

This paper analyzed the seismic force modification factor R of strength degrading modified elastic-perfectly plastic (EPP) model, bilinear elastic (BIL) model and shear-slipped elastic-plastic (SSP) model for different site and ductility factor. The system coefficient spectra of base shear were constructed to analyze the influence of the degradation of strength on seismic force modification factors. An ideal elastic-plastic model is proposed which is equivalent to the degradation model. Results reveal that the strength degradation has almost no influence on the R spectra of BIL and SSP model, but for modified EPP model, its influence increases with the degradation and cannot be neglected. When taking the strength degradation to define the ductility factor in practice in modified EPP model, it is necessary to adopt a ductility-definition-related strength reduction factor. For the strength degrading system, the strength demand and the deformation-capacity demand are found to be αEK times of the ideal elastic-perfectly plastic model.