Experimental Study On The Behavior Of High-strength Lightweight Aggregate Concrete Filled Steel Tube Under Axial Compression

High-strength lightweight aggregate concrete filled steel tube (HSLACFT) is a sort of new type concrete filled steel tube (CFST) which use lightweight aggregate concrete (LWAC) instead of common concrete. HSLACFT has the excellence of not only high-strength lightweight aggregate concrete but also CFST, and overcomes the limitations of LWAC. The diversified mechanical properties and failure mode of HSLACFT stub columns under axial compression are roundly studied through experimental investigation. At the same time, the influence of loading conditions on the behavior of lightweight aggregate concrete filled steel tube stub columns under axial compression is discussed. The primary contents are as follows-.1.33 stub column specimens of high-strength lightweight aggregate concrete filled steel tube which have diverse parameters are studied experimentally. The parameters are measured respectively during the experimental process, such as bearing capacity, deformation, strain and so on. It concludes that the elastic ratio, strength, and plasticity of concrete are improved more or less under the restriction of steel tube, and confining ratio is a significant parameter to the mechanical properties of the HSLACFT stub columns, furthermore, the ultimate capacity of HSLACFT is close to that of the normal concrete filled steel tube.2. In this paper the longitudinal strain (deformation) curves, horizontal deformation, overall deformation characters, failure mechanism and failure modes of the lightweight aggregate concrete filled steel tube stub columns under axial compression are observed and studied. The investigation showed that not only the confining ratio but also the strength of lightweight aggregate concrete influence the characteristic of deformation and failure modes of HSLACFT. And the shear failure may be the failure modes as the lightweight aggregate concrete strength increases.3. Based on the experimental study of 27 lightweight aggregate concrete filled steel tube (LACFST) stub columns under three types of loading conditions, influence of the loading conditions on the failure pattern and mechanical behavior of the specimens are studied. The main experimental parameters are different grades of lightweight concrete intensity and cross sectional sizes of steel tubes. The three loading conditions are: 1. Compressive load acts on concrete only; 2. Steel tube and concrete subjected to compressive load simultaneously; 3.Compressive load acts passing through the roller located at the whole cross section. The test results indicate that the deformation behavior of the specimens is substantially influenced by the loading conditions which affect the ultimate carrying capacity a little. Whatever the loading conditions, the LACFST stub columns can deform plastically with remaining great carrying capacity.