| The circular concrete-filled circular steel tube member is a new type of composite steel tube concrete member,which is formed by pouring concrete between the inner core of two circular steel tubes placed in the inner and outer layer and the inner and outer layers of the inner and outer steel tubes at the same time.Thereby,the mechanical properties of the members are improved effectively without changing the size of the outer steel pipe.With the development of modern buildings towards the direction of long span,light weight,towering and high performance,the concrete filled circular steel tube structure has also attracted more and more attention in the field of engineering application as a new type of composite structure.However,in the normal use stage of the whole life cycle,engineering structures will inevitably be affected by accidental impact,such as the impact of derailment trains on adjacent buildings,the impact of wrecked aircraft on high-rise buildings,the accidental impact of ships on bridges and so on.Once a strong impact occurs,it may lead to a serious safety accident.Due to the uncertainty of impact,how to evaluate and improve the crashworthiness of the building structure has become a new problem to be solved urgently.In this paper,ABAQUS software is applied to make a finite element analysis on the mechanical response process and crashworthiness of concrete-filled circular steel tube members under low speed transverse impact.The specific research contents are as follows:(1)Through using ABAQUS software,the finite element model of concrete-filled circular steel tube members with circular steel tubes under transverse impact is established,which considered the contact relationship between steel tube,drop weight and concrete,and properly selected the material model of inner and outer layer steel tube and concrete under dynamic loading.Then the accuracy of the established finite element model is verified by using the test data and the typical test data of concrete filled steel tubular(CFST)and hollow sandwich concrete-filled steel tube(CFST).The results show that the finite element calculation results are in good agreement with the experimental results,so the finite element model can be used to analyze the crashworthiness of concrete-filled circular steel tube members.(2)With regard to the verified model,it is necessary to make an analysis of the working mechanism of circular steel tubular concrete filled steel tubular members under the effect of transverse impact load.The main content of the analysis includes the failure mode and energy dissipation of the member,as well as the whole process analysis of the dynamic response of the component is carried out.Then the main factors affecting the mechanical properties of concrete-filled circular steel tube members under transverse impact are analyzed.The results of parameter analysis show that increasing the yield strength and steel content of outer steel tube can effectively improve the crashworthiness of the component.When the ratio of inner diameter and outer diameter of the member is 0.6 ~ 0.8,the member has better crashworthiness.(3)According to calculation method of static limit bending moment of concrete-filled steel tubular members,combined with numerical simulation and theoretical analysis,therefore the static limit bending moment calculation method of concrete filled circular steel tube members can be obtained.The finite element modeling method in(1)is used to calculate the dynamic ultimate bending moment of concrete-filled circular steel tube members.The calculation formula of dynamic ultimate bending moment of the member could be obtained on the basis of a lot of numerical simulation.And by means of the simplified analysis model of "equivalent plastic hinge",the calculation method of maximum deflection has been developed after the impact on the mid-span section,which provides a reference for engineering practice. |
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