Resistance Performance Of Centrifugal Concrete-Filled Steel Tubes Under Complex Loads

Centrifuge concrete-filled steel tube is a special kind of composite structure. It is made of a thin-wall steel tube and a centrifugal concrete tube inside. Because of its advantages,such as good plasticity and elasticity,good rigidity and small weight,it has been widely used in engineering fields. In the real practice,there are always combinations of different loads on a structural member. Bending and torsion is one of these combinations. Heretofore most of researches about centrifugal concrete filled steel tubes have focused on performance of such a structural member under single loads and there has few researches about performance under complex loads. Therefore to carry out studies on centrifugal concrete-filled steel tubes under complex loads is of great value to popularize application of this structure.In this thesis,the resistance performance of concrete-filled steel tubes under simple load is summed up first. According to the resistance expressions under press and bending,a concise formula of resistance under torsion is deduced on the ground of two former formulae. The format of this formula is of good similarity with that under press and bending.An experimental study on concrete-filled steel tubes under bending and torsion is conducted. The experimental stress analysis shows that values of practical critical stress of the steel tube correspond well with MISES Yielding Rule. Finally,a correlative equation about bearing capacity of this structural member under bending and torsion is deduced,which may provide design of such structural members a valuable reference.To imitate centrifugal concrete-filled steel tubes used in real structures,three-dimension models are built up by using finite element method. The resistance performance of this structure under complex loads is studied. It shows that the result of resistance under bending and torsion by this method is almost same as that of experiments. Correlate equations of bearing capacity of this structure under complex loads are deduced.Four expressions of bearing capacity of this structure under complex loads,which are press,bending and torsion,are deduced in the end.