Analysis On Preheating Self-stressing Concrete-filled Steel Tube By Theory And Numerical Simulation

Concrete-filled steel tube structure is a composite structure that formed by filling concrete to the thin-walled steel tube. This structure integrated the advantages of the reinforced concrete structure and steel tube structure, and avoided the disadvantages of the two at the same time. Concrete-filled steel tube is widely applied in building and bridge engineering. It is applied in the following bridge structures: the girder and cable tower of suspension bridge, the girder of cable-stayed bridge, the girder and pier of beam bridge, the arch rib of arch bridge. Especially, the application scale of concrete-filled steel tube arch bridge is largest. Despite the higher bearing capacity and the better plasticity and toughness of concrete-filled steel tube structure, it shows that the interspace generating is common between steel tube and core concrete, and the size of the interspace is different, according to the test to many concrete-filled steel tube arch bridge inland.The "hooping effect" will not be able to play after the interspace generating between steel tube and core concrete, which will affect the stiffness and section stress distribution of arch rib, and will produce certain effect to mechanical property and bearing capacity of concrete-filled steel tube arch bridge. The study of these problems is very urgent and necessary.In order to solve the problem of interspace generating between the steel tube and the core concrete under long-term services of the concrete-filled steel tube structures, this paper puts forward a method that preheating the steel tube during the pouring and curing of core concrete, by which the steel tube produces an initial hooping force(namely self-stress) to the core concrete after cooling. Theory and numerical simulation analyses for self-stressing status of concrete-filled steel tube are used in the article aimed at this method. The main conclusions are obtained as follows:(1) Preheating self-stressing concrete-filled steel tube is feasible in theory.(2) According to the different requirements of the residual hooping force, the preheating temperature is about 25℃ to 45℃ higher than environment temperature.(3) The ratio of self-stress that produced by preheating method to material strength is not too large. Checking calculations should be conducted according to the designing load.