Analysis On The Bearing Capacity Of Lightweight Concrete Filled Steel Tube Columns

The lightweight concrete filled steel tube columns have many advantages, such as high-capacity, self-respect light, seismic performance, and excellent fire-resistant properties and improve the environment and so on. The text has a research about the bearing capability of lightweight concrete filled steel tube columns. The obtained results are satisfied and can be used as basis for the design process of lightweight concrete filled steel tube columns.At first, the bearing capability of lightweight concrete filled steel tube columns subjected to axial compressive loading was studied based on the Twin Shear Unified Strength Theory. The calculation formula was derived and the effect of the intermediate principal stress, the confinement effect between the strain-constrained concrete cylinders and the steel tube, was considered sufficiently. Based on criterion, to consider bearing capability reduction factor, witch the bearing capability of long columns obtained.Second, the ultimate load calculation formula for the above multibarrel tube-confined lightweight concrete columns under axial compressive is derived based on the Unified Strength Theory in the paper.Third, the Von Mises failure criterion and isotropic hardening stress-strain relationships have been used for steel and the William-Warnke criterion and elastic-plastic stress-strain relationships used for concrete in term of ANSYS9.0. The 3D models of the concrete filled double skin steel tube (CHS inter and CHS outer) and (CHS inner SHS outer) are founded by 3D solid elements. The capacity behavior and ultimate load of above two multibarrel tube-confined lightweight concert columns are analyzed under axial compressive. The load-displacement curves are obtained. Several conclusions can be obtained from the results of this paper: (1) When the double skin (CHS inner and CHS outer) steel tube columns were loaded under the ultimate bearing capacity, the inner and outer steel tube has yielded. The maximal stress of outer steel is close with the two ends. The stress of outer steel tube shows symmetry distributing. The sandwich concrete of the outer steel tube is crushed, but its of the inner steel tube is not crushed. The phenomenon shows the reinforcement effect of the inner steel tube. (2) When the double skin (CHS inner and SHS outer) steel tube columns were loaded under the ultimate bearing capacity, the stress of the four surface of the outer steel tube is distributed the same each other. Under the ultimate load, the sandwich concrete is crushed and the inner and outer steel tubes are yielded. (3) The load-displacement of the above section shape show that the steel tube is not important factor for the advancement of the ultimate bearing capacity. And the steel tube has a sufficient restriction to sandwich concrete under the ultimate load.