SEISMIC RESPONSE OF COMPOSITE FRAME WITH CFST COLUMNS UNDER FAR-FIELD GROUND MOTION

A typical 10-story composite frame with concrete filled steel tubular(CFST) columns was designed to study the seismic response under far-field ground motion.28 far-field(10km) ground motion records in the strong motion database from the Pacific Earthquake Engineering Research(PEER) Center were used for the ground motion input.The sites were divided into four types,named A,B,C and D respectively,according with the classification of United States Geological Survey(USGS).The nonlinear fiber beam-column element was used to simulate the CFST columns and beams,respectively,and the elastic-plastic dynamic time history analysis was performed using OpenSees under meeting more and rare earthquakes of the seismic precautionary intensity in 8 degrees.The results were compared with that of pushover analysis.It is shown that the seismic response of the composite frame exhibits some regularity under different sites and ground motions though the results are discrete.The inverted triangle lateral load pattern is more similar to the result of dynamic time history analysis than the uniform distribution lateral load pattern for the regular composite frame structures,thusly the inverted triangle lateral load pattern should be used to the pushover analysis for the composite frame with CFST columns.