Study On Numerical Analysis Method Of Interfacial Bonding Performance Of Self-Stressing Concrete Filled Steel Tube

The development of society and the progress of science and technology are always closely related to people's life,and also benefit people's life in all aspects.At the same time,people are increasingly demanding the living environment.The main manifestation is that buildings are developing towards higher height,longer span and richer functions.However,ordinary reinforced concrete structures can not meet people's requirements for higher height and longer span of buildings.Therefore,it is imperative to explore and study new building structures.At present,steel-concrete composite structures are being more and more widely used in building structures,in which concrete filled steel tube plays an important role in the application of long-span bridge structures.The main reason why concrete filled steel tube can give full play to the excellent performance of the two materials is that the core concrete is in a three-dimensional compressive state under the restraint of steel tube,which can improve its compressive strength.Hardening of core concrete can delay the buckling rate of steel tube wall However,during the hardening process of ordinary concrete filled steel tube,the core concrete will shrink chemically,which will lead to the void of concrete filled steel tube and deteriorate the interfacial bonding performance.In this case,researchers have proposed that the self-stressing concrete filled steel tube,which is filled with self-stressing concrete instead of ordinary concrete.At present,some experimental results have been obtained,but the corresponding numerical simulation analysis is not enough.Therefore,based on the experimental study of the interfacial bonding performance of concrete filled steel tube,the following works have been done in this paper:(1)The relationship between radial self-stress and circumferential self-stress of core concrete caused by temperature rise is deduced.The relationship between the amount of expansive agent and circumferential strain of steel tube in the whole process is obtained by curve fitting of the experimental data of concrete filled steel tube with expansive agent.Finally,the relationship between the amount of expansive agent and the temperature required to achieve the same effect is determined.(2)The interfacial bonding performance of concrete filled steel tube is simulated by core concrete heating and Combin39 spring element respectively and compared with the push-out test of self-stressed concrete filled steel tube.The results show that the simulation effect of spring element on the load-displacement-curve of the whole process of push-out test of self-stressed concrete filled steel tube is better than that of core concrete heating.(3)Based on the axial compression test of self-stressing concrete filled steel tube,the finite element analysis of axial compression considering the interfacial bonding performance is carried out.It is further verified that the method of simulating expansion stress by means of contact element heating is feasible.The simulation results of the increase of ultimate axial compression load of self-stressing concrete filled steel tube are in good agreement with the experimental results.