Study On Dynamic Response Of Reinforced Concrete Beams Under Falling Impact

Under impact,reinforced concrete beams will produce completely different responses under general dynamic loads,which has attracted wide attention.In this paper,the dynamic response and failure characteristics of reinforced concrete box girders impacted by falling objects are studied by means of numerical analysis.The influence law of dynamic response and the transmission law of impact force of beams under impact are studied from two aspects: simply supported beams with ideal elastic materials and reinforced concrete beams.The impact load acting on different positions of box girders is also studied according to the structural characteristics of box girders.The law of transverse conduction.The main research contents include the following aspects:(1)Considering the three factors of velocity,mass and impact location,the influence law of dynamic response of ideal elastic simply supported beam is studied.The results show that the dynamic response of the beam under impact can be divided into two stages: the initial stage of action and the later stage of action.The initial stage of action is before the action effect is transmitted to the support,and the peak value of action force and deflection occurs after the action effect is transferred to the support in the later stage.The effect of action is similar to that of ordinary dynamic load.(2)Taking reinforced concrete rectangular beams as objects,the influence of velocity,mass and impact location on the dynamic response of reinforced concrete rectangular beams under two different failure states after impact is discussed.The results show that under impact,when the reinforced concrete beam is in the plastic hinge state,the damage of the beam is mainly divided into two stages.In the initial stage of impact,the beam is mainly damaged by shear;then when the impact force is transmitted to the support,the dynamic response of the beam is in the second stage,that is,the beam is mainly damaged by bending.(3)Taking reinforced concrete box girder as an object,the transverse transmission law of dynamic response of impact on the top and web of box girder is studied respectively when falling objects impact on the top and web of box girder.The results show that when the impact speed and mass increase,the impact of falling objects on the roof of reinforced concrete box girder will produce local shear failure,consume impact energy,and make the impact response unable to transfer completely from the roof to the web.The larger the impact speed and mass,the smaller the transverse transmission.When falling objects impact on the web of one side of the box girder,the impact effect of the box girder will be partly transverse.When the impact velocity increases,the impact side web gradually develops from bending failure to Bending-shearing cross-section failure,while the non-impact side web is mainly bending failure.