CROSS SECTIONAL SHEAR STRAIN DISTRIBUTION OF RECTANGULAR CONCRETE FILLED STEEL TUBE COLUMNS SUBJECTED TO TORSION

Tests on concrete filled steel tube columns with rectangular section subjected to pure torsion and compression-torsion were carried out, and the hysteretic curves of torsion moment versus rotational angle were obtained. Based on the principles of material mechanics, the relations between the torsion curvature of the section and the shear strain of the fiber at the section were established. Then the cross sectional strain distribution at the rectangular section of concrete filled steel tube columns was analyzed. The three-dimensional refined finite element model was also built for purpose of verification. At last, the matrix forms of the relations between the torsion curvature of the section and the shear strain of the fiber at the section were derived and introduced into the fiber beam model considering torsion effect. The comparison between the test results and calculation results shows that the fiber beam model considering torsion effect has high modeling efficiency and accuracy for predicting the torsion behavior of concrete filled steel tube columns with rectangular section, and is suitable for analyzing the dynamic response of structures subjected the combined cyclic loads due to earthquake excitations.