Study On Failure Mode And Dynamic Response Of Steel Beam-column Under Impact

H-shapes, which are commonly used for load-bearing members in steel structural engineering, may suffer from accidental impact duiring its service period and thus results in huge loss of life and property. It is significant to study the dynamic response, failure mode, residual bearing capacity of pre-loading steel column under impact load for the anti-collision design of steel structure. In this paper ABAQUS software was used to perform the investigation on the case that H-steel beam-column is impacted. The main work and conclusions are as follows:The finite element model of axially compressed Q235 H-shaped steel columns was established by using five common constitutive relations and the numerical simulation results were compared and analyzed. It shows that whether to consider the strain rate greatly affect the numerical simulation results; the simulation results of constitutive models are related to the level of impact kinetic energy; the numerical simulation results of different constitutives on the local defonnation of the impact area are close, the farther away from the impact area, the difference between the numerical simulation results tends to increase and from the local to the whole the numerical simulation results show that the relative deviation between the different constitutive models tends to increase.The failure modes of the beam-column subjected to the transverse impact are studied and parametric studies on the dynamic response are performed. By investigating the conversion of the system energy and the proportion of the hourglass energy, the rationality of the numerical simulation scheme is verified. The failure modes of beam-column under transverse impact are analysed, and parameters studies are proformed. The results show that the failure mode of H-steel beam-column is global plastic buckling which is mainly caused by local buckling of the flange of H-steel beam-column; the failure of beam-column mainly depends on the kinetic energy of the impact and also concerns with the impact position, axial force and bending moment.The increase of impact energy (including impact mass and impact velocity), impact position and axial pressure will intensify dynamic response of the beam-column; When the moment is imposed on the column being axially compressed, the combined axial pressure and moment at the beam-column end which can reduce the dynamic response of the beam-column exists, but with the increase of the moment. the deformation of the column increases until it is damaged.An explicit-implicit sequence numerical simulation scheme is proposed to simulate state of the impact damage and the bearing capacity of H-shaped steel columns with impact damage was analyzed. It is found that the impact kinetic energy and the impact position are the key factors influencing the stiffness of the impacted steel column. When the plastic is fully developed, the final bearing capacity of the impacted steel column is the same; the global plastic buckling occurs before the flange region at the center and the foot of the damaged column is locally buckled. When impact-load state is not close to the critical state at which the steel column fails during the impact, the residual bearing capacity factor decreases with the impact kinetic energy,the distance from the impact point to the fixed end, the axial pressure and the bending moment,but a huge drop of the residual bearing capacity is caused when close to the critical state.Howevre in contrast the effect of bending moment on the residual bearing capacity is minimal.The most unfavorable position of the impact is located slightly above the half of the column height. The different velocity and mass combinations of the impact kinetic energy have little effect on the residual bearing capacity factor but large tonnage impact is the most unfavorable combination. The relationship between the residual bearing capacity factor and the axial displacement increment due to impact is obtained by fitting.