Study On The Bearing Capacity Of Middle Long Lightweight Aggregate Concrete Filled Steel Tube Columns

Lightweight aggregate concrete filled steel tube (LACFST) is a sort of new type concrete filled steel tube (CFST) which use lightweight aggregate concrete (LWAC) instead of common concrete. Comparing with ordinary CFST, LACFST has the excellence of not only high strength and good ductility, but also reduce the dead weight about 20 %. Applying LACFST in bridge structure can light the dead weight and reduce the load on foundation, was accorded with the developing trend of modern bridge structure.24 specimens of lightweight aggregate concrete filled steel tube middle long columns which have diverse parameters are studied experimentally. The diversified mechanical properties and failure mode of LACFST middle long columns under axial compression are roundly studied through experimental investigation. At the same time, by discuss the difference of the bearing capability between LACFST and ordinary CFST middle long column, the working mechanism of CFST middle long column under axial compression was studied.Finally, FEM software ANSYS was used to simulate the bearing capacity of LACFST and CFST middle long columns.The primary contents are as follows:1. The experiment shown that the bearing capacity of LACFST middle long column would not lower than that of CFST. All the middle long specimens were yield in the elastic-plasticity stage. Bounds slenderness ratio among axial compression middle long columns and long columns was 79, less then that of ordinary CFST with the same parameter.2. The contrast and analyse of stability factor among 3 sorts of CFST shown that high stability factor appeared in the specimens with higher peak strain of core concrete. The mechanism of CFST middle long column was studied by analyzing the cross section and tangent modulus theory. The conclusion shown that high limit of proportionality appeared in the specimens with higher peak strain of core concrete, as a result the stability factor of CFST middle long column increased.3. The stability factor of LACFST and ordinary CFST was calculated by the numerical simulation using FEM software ANSYS. The mechanism of CFST middle long column that extracted was proved. It was feasible to use beam element with constitutive relationship base on unification theory to simulate the bearing capacity in elastic-plasticity stage.Base on the experimental study of LACFST middle long column in axial compress and contrast with ordinary CFST, the mechanism of CFST middle long column was studied. The results of experiment can be explained properly by this theory.