Study On Performance Of Square Hollow Steel Tube-RC Laminated Members Under Low Velocity Lateral Impact

Hollow steel tube-reinforced concrete(HSTRC)laminated structure,as a new form of composite structure,consists of outer RC and inner core hollow steel tube.HSTRC combines the advantages of RC and steel materials,and has good mechanical properties and workability so that it has wide application prospect and potential advantages in the building structures.At the same time,the impact load has become an important factor which endangers the stability of the building structures and the safety of personal properties.However,researchers are mainly focused on the mechanical properties under static load,and the research under dynamic load is still in the preliminary exploration stage at present for HSTRC.Therefore,the experimental research and numerical analysis of HSTRC members under lateral impact load are carried out in this paper.The main contents are as follows.Firstly,experimental work of HSTRC under lateral impact load was conducted with the self-designed drop hammer rig.The main parameters of specimens include the impact height,the boundary condition and the axial compression ratio.Failure modes,impact force curves,mid-span deflection curves and axial force curves were recorded in the tests.The test results showed that HSTRC specimens have flexure failure modes under lateral impact load.Then a finite element analysis(FEA)model was established to predict the impact behavior of HSTRC members,in which the strain rate effects of RC and steel materials,the contact behavior of different instances of the model and the boundary condition were considered.The accuracy of the FEA model was verified in failure modes,impact force curves,mid-span ultimate deflection and energy change.It turned out that the FEA model can effectively simulate its mechanical behavior under lateral impact load.Finally,the influences of main factors on the impact resistance of HSTRC members were analyzed according to the FEA model.It was shown that yield strength of steel,concrete strength,ratio of reinforcement and steel ratio can affect impact resistance of HSTRC members respectively.