RESTORING FORCE CHARACTERISTIC AND ULTIMATE BEHAVIOR OF CONCRETE FILLED STEEL TUBE COLUMNS USING ULTRA-HIGH STRENGTH STEEL H-SA700

In this paper, the cyclic behavior of concrete filled steel tubes (CFTs) using high strength (HS) steel “H-SA700” under combined constant axial and flexural loads was investigated experimentally. In the CFTs made from HS steel, the compressive strength of concrete was reached before steel yielding. Thus, a design method which takes into account this phenomenon for estimating the yield strength capacity of HS steel CFTs was proposed. Good agreement was observed between the test and estimated values. In addition, after ultimate strength reached the inelastic behavior of HS steel CFTs was similar to that of conventional ones.