SEISMIC RESPONSE AND CONCRETE-TO-TUBE STRENGTH RATIO OF CONCRETE FILLED STEEL TUBE FRAME

Seismic response and damage of concrete filled steel tube frame (CFT frame) are investigated in relation with the concrete-to-tube strength ratio (p) of CFT column. One of the authors has proposed the numerical analysis method to predict the damage of CFT frame under extremely strong ground motion by introducing the damage ratios of steel tube crack and local buckling of CFT column. By the use of the presented analysis method the seismic responses of CFT frame have been calculated and the damage ratios of CFT frame to collapse dynamically are obtained quantitatively. From the results it is shown that the calculated damage ratios of CFT frame are closely related to the value of p and p=11.0 is proposed as the critical value in the earthquake resistant design of multi-story CFT frame.