Study On Performance Of Steel Reinforced Concrete Members With Inner Cruciform Section Steel Under Lateral Impact

Steel-reinforced concrete structures(SRC),due to its excellent bearing capacity and seismic performance,has been widely used in super high-rise structures,bridge structures,and buildings in earthquake zones.SRC members are the chief load-bearing components in structures and it will be extremely dangerous when these components subjected to impact loads because of the continuous collapse of the structure it brought.Previous studies focused on the basic mechanical properties and seismic performance,and there are few reports on the impact resistance of SRC structures.This work investigate the dynamic performance of steel-reinforced concrete members under lateral impact are studied.The main research work and achieved outcomes are as follows:1.An experimental programme was carried out through a high performance drop hammer machine.The dynamic response of seven SRC members with double H-shaped steel were described and discussed with emphasis the effect of the impact velocity,boundary conditions and axial compression ratio.The deformation-process,failure mode,impact force curve,mid-span deflection curve and the axial force curve were obtained in the tests.2.A finite element model of the SRC structures subjected to impact loading was established.The strain rate effect of the material and the damage of the concrete,the contact between the steel and concrete and other components were considered.Model experiments were conducted to explore the influence of unit type and grid size on the calculation results.Subsequently,a method of coupling axial force and impact in explicit dynamic FEM was introduced.The test results in this paper and other typical test data were used to verified the reliability of the FEM.3.The working mechanism of steel-reinforced concrete members under lateral impact was investigated though the finite element model,including the failure mode of each component,stress and strain development,energy distribution and so on.The result showed that the H-shaped steel and concrete are the chief dissipative members,the plastic strain of the steel bar and steel is fully developed,and the material strain rate has significant effect on the dynamic response of SRC members under impact load.The development rules of impact force,inertial force and support force are analyzed and the equivalent bending test was conducted through the FEM.4.The effect of parameters on the impact resistance of steel-reinforced concrete members was systematic studied,including load parameters,material parameters,geometric parameters and boundary conditions.The results showed that,in the previous application range of the project,the boundary conditions,steel ratio of profile steel,selection of steel materials and the spacing of stirrups are the main parameters that affect the impact resistance of steel reinforced concrete members.5.Based on the results of parameter analysis,a method for evaluating the impact bearing capacity of steel-reinforced concrete is proposed.A regression calculation method is used to obtain a calculation formula for the impact bearing capacity amplification factor and its accuracy is verified using the FEM results.Combined with the code for design of composite structures,the calculation method of the bending and shear bearing capacity of steel-reinforced concrete members is presented.