Analysis Of Damage Effects Of A Prestressed Reinforced Concrete Hollow Beam Subjected To The Synergistic Effects Of Blast And Fragments

In recent years,the number of large-span buildings in China has increased dramatically,especially for long-span bridges,which has promoted the development of prestressed concrete.However,the frequent occurrence of terrorist attacks and accidents in daily production has forced structural designers to consider the anti-explosive design of structures.Prestressed concrete beams are the main load-bearing members.Once explosion occurs,they will inevitably cause serious economic losses and a large number of casualtiesso it is of great practical significance to study the dynamic response and damage of prestressed RC beams under blast loading.Based on the nonlinear finite element software LS-DYNA,the dynamic response and damage of prestressed RC hollow beam under the combined effect of near-explosion shock wave and prefabricated fragment are simulated.The main research work and the conclusions are as follows:(1)A finite element model consisting of explosives,fragments,air and prestressed reinforced concrete hollow beams and end restraints was established.The simulation was carried out by simulating the impact of shock waves on prestressed plates and explosive-driven fragments to verify the reliability of material constitutive models,contact algorithms and technical routes.(2)In order to study the mechanism and difference of the fragmentation and shock wave,this paper establishes the finite element model of the prestressed reinforced concrete hollow beam under the action of the near-explosive shock wave load alone,the prefabricated fragment group load alone and the combination of shock wave and fragment load.The results show that the structure tends to have obvious local damage when there are fragments,so the local armor piercing effect of the fragments should be considered in the anti-explosion design.(3)The influence of the characteristics of the prestressed hollow beam on the blast resistance was studied.The results show that: with the increase of tensile control stress,the anti-explosion performance of the component increases;the anti-explosion performance is basically the same when the same tension control stress acts,even if there are different levels of stress loss;the concrete strength cannot increase the anti-explosion performance significantly;compared to the others,the anti-explosion performance of the components is best when the reinforcement ratio of ordinary steelbars is 0.012;with the increase of the spacing of stirrups,the anti-explosion performance of the component weakens obviously.(4)The influence of external load parameters on the anti-explosion performance of the components was studied.The results show that when the proportion distance is the same,the explosive quantity plays a leading role in the structural damage;when the proportion distance is different,the explosive quantity plays a leading role when the proportion distance is small,but the effect of the two is basically the same as the proportion distance increases to 0.38.When the explosive moves along the width of the beam,the eccentric load will cause the member to be distorted and further damaged.When the thickness of the fragment and the total volume are kept constant,the damage of the fragment increases the damage of the structure first and then weakens;When the cross-sectional area and the body state are constant,within a certain range,the increase of the quality of the fragment will make the structural damage more serious.