Research On The Behavior Of Core Lightweight Aggregate Concrete Under The Confinement Of Steel Tube

With the development of the modern civil engineering structure towards lightweight, high strength, long span and high-rise, the construction material and structure are higher required. The lightweight aggregate concrete which has the advantage of high strength, lightweight and durability combined with the good mechanical behavior of the concrete filled steel tubes, the lightweight aggregate concrete filled steel tubes (LWACFST) are widely used in the engineering construction. However, due to the little systematical research on the LWACFST, which affects the design of the structure and its application and development.Regard the core lightweight aggregate concrete under the confinement of steel tube as the research object. 6groups of 18 lightweight aggregate concrete confined by the steel tubes as well as 42 LWACFST stub columns are tested, and the mechanical behavior of the light weight aggregate concrete confined by the steel tubes under axial compression is discussed.Firstly, 6 groups of 18 light weight aggregate concrete confined by the steel tubes are tested to discuss the concrete strength, steel ratio of the specimen which influence the carrying capacity of the core lightweight aggregate concrete, the relation curves of stress-strain and the failure mode. The experimental and theoretical study indicates that the deformation and ductility behavior of lightweight aggregate concrete under the confinement of steel tube are obviously improved and the strength is largely enhanced, though the confinement effect is lower than the common concrete. And the strength criterion of the lightweight aggregate concrete under three-dimensional compression is established according to the test results.Then, combining the test of 42 LWACFST stub columns under axial compression and using the method of separation analysis, the test data of the stub columns is analyzed. Base on the study of the stress variety of the steel tubes and the core lightweight aggregate concrete under compression, the constitutive relation of the concrete is established. Its computed results are well agreed with the tested oneby the separation analysis.At last, according to the theory of limit equilibrium, the calculation formula of the carrying capacity of the LWACFST stub columns subjected to axial compression is derived. The load-deformation relational complete curves of the LWACFST stub columns is analyzed using the nonlinear analysis program. All the calculated results are in good agreement with the tested one.