Seismic performance evaluation of nonseismic designed flat-plate structures

In this study the seismic performance of flat plate system structures designed without considering seismic load was investigated. Both the capacity spectrum method provided in ATC-40 in 1996 and nonlinear dynamic analyses were carried out to obtain maximum interstory drifts for earthquake loads. Also, a seismic performance evaluation procedure presented in FEMA-355F in 2000 was applied to evaluate the seismic safety of the model structures. The analysis results showed that the maximum interstory drifts of the nonseismic designed flat-plate structures computed by the capacity spectrum method and the nonlinear dynamic analysis were smaller than the limit state for the collapse prevention performance level. However, the results of the FEMA procedure showed that the model structures did not have enough strength to ensure seismic safety.