Empirical formula of fundamental period for steel structure based on seismic response record

To improve the seismic design of steel frame structures, the empirical formula for evaluation of fundamental periods of steel frame structures was investigated and a new formula was presented in the paper. A total number of 36 moment resisting steel frame structures were selected for the statistical analysis, and all the structures obtained seismic response records during past earthquakes. The fundamental periods of all structures before damaged were identified by using ARX method, and the new empirical formula for fundamental period of steel frame structure was obtained through nonlinear least square regression. The result shows that the fundamental period of steel frame structure can be expressed in terms of the height to the power of 0.6 and multiplied by the modified factor 0.12. The proposed empirical formula can be referenced for the seismic design code revision, steel frame structures seismic design and related researches.