Dynamic Response Of Steel-concrete Composite Structure Under Vehicle Impact

In recent years,collisions between vehicles and buildings(structures)have occurred frequently,which caused a large deal of property damage and casualties.In order to research the dynamic response of Steel-concrete composite structure under the impact of a vehicle,this papers conducts a series of numerical simulations based on the large nonlinear explicit analysis software LS-DYNA,and has verified the validity of the model,the main research contents are as follows:(1)The impact force curve of a vehicle can be roughly idealized into four phases:elastic impact phase,peak phase,stabilization phase and release phase.Reinforced concrete column,steel reinforced concrete column and concrete filled steel tube column.Parametric analysis was carried out on the factors affecting the impact resistance of square frame columns,such as vehicle type,vehicle speed,axial compression ratio of frame columns,impact angle and offset distance.The plastic damage and failure modes of three frame columns under vehicle impact were discussed.The result show that the damage pattern of frame columns differed under the impact of different vehicle models.The reinforced concrete column and the steel reinforced concrete column showed local compression failure under the impact of the mini-vehicle;when the light truck hits,the top of the column shows oblique shear failure,and the bottom of the column shows bending shear failure.Both of them showed bending shear failure when the medium truck collides.The tubular concrete columns were basically undamaged by the impact of the mini-truck.Under the impact of light and medium-sized vehicles,the failure mode is bending failure and shear failure.(2)The impact force time history curve of the frame column increases with increasing velocity.Axial load can be reduced to some extent by the appearance of concrete cracks,which is beneficial to the shear failure caused by impact.Not the greater the peak impact force of the forward impact,the more remarkable the dynamic response of the vehicle,and the lateral impact often caused more damage to the vehicle.When the equivalent static value of medium-sized vehicles reaches 70 kilometers per hour,Highway specification cannot meet the requirements of equivalent static.(3)Numerical analysis was performed for four conditions such as long-sided center column,short-sided center column and corner column of the impacted Steel Tube Frame Structure.It was found that under the impact of the vehicle,even though the concrete material was shattered and had failed,the frame structure was only partially deformed due to the restraint of the steel tube,which showed a slight swelling on the three non-collision surfaces and was not seriously damaged.The impacted frame columns mainly exhibited a bending-shear damage mode,with severe damage at the beam-column joints,in the mid-span of the frame girder and at the corners of the each concrete floor.By comparison,the best impact resistance was found when impacting the short-sided centre column B1,followed by the long-sided centre column A5,followed by the corner column A1,with the long-sided centre column A3 having the worst impact resistance.(4)The following deformation limit conditions are proposed to evaluate the impact resistance of the frame according to the seismic code of the structure: at the first floor column collision site,the ratio of its horizontal displacement to the height of the story should be no greater than 1/50,while the ratio of the maximum horizontal displacement at the top of the the column to story height should be no greater than 1/200.Formulas are proposed for the calculation of energy absorbing capacity and the expression value of the collision force is proposed.A smaller energy absorbing capacity of the structure during the collision and a larger value of the collision force means that the collision load has less impact on the frame structure,the less deformation of the structure and the better,and then the better ability against collision.