The Study of the Safety Factor of the Pushover Analysis Procedure Based on the Capacity Spectrum Method

The Study of the Safety Factor of the Pushover Analysis Procedure Based on the Capacity Spectrum Method

At present, engineers often use pushover analysis based on the capacity spectrum method to work on detailed seismic evaluation of structures in Taiwan. The performance target of the ground acceleration is used to compare with the site peak ground acceleration of a design earthquake with a 475-year return period to evaluate the sufficiency of a structure’s seismic capacity. These evaluated results are too conservative as stated in FEMA 440. In this report, the nonlinear dynamic analysis of a single degree structure is used to study the inherent safety factor of the capacity spectrum method and its relationship with the elastic stiffness of the structure, the dispersive hysteretic energy, and the characteristic of input seismic record. From the analysis results, this safety factor is found to be larger than 2 and to have a larger value for less stiff structures. It is also found to be independent of the dispersive hysteretic energy, and to be influenced by the characteristic of the input seismic record.