Analysis Of Impact Resistance Behavior Of New Steel Node-connected Prefabricated Concrete Frame Substructures

In recent years,prefabricated buildings have been vigorously promoted in China.They have the advantages of high construction efficiency,environmental protection and greatly reducing manual dependence.Beam column joint is the key part of fabricated structure,which plays a very important role in the mechanical performance of the whole structure.Once the joint is damaged,it can lead to the overall collapse of the building.Reasonable design of beam column connection mode and making the fabricated structure safer,more reliable and more convenient for construction through new materials and technologies are the research hotspots in this field.At present,there are no relevant regulations on the design of civil structure under dynamic load in China.At present,for the research of prefabricated structural joints,scholars at home and abroad mainly focus on the strength and seismic performance of joints,and there is less research on the impact resistance of joints.In the multi-storey civil building structure,the impact on the structure caused by the falling of heavy objects such as instruments and equipment,or the damage and falling of the building structure under accidental extreme load,or even the falling of the whole floor,often occur.The impact of falling objects on the lower structure will cause the damage of beam members or beam column connections,and eventually lead to continuous collapse.Therefore,it is particularly important to study the impact resistance of prefabricated concrete frame structures widely used in civil buildings.In this article,for the fabricated concrete frame structure connected by new steel joints,using the finite element software ABAQUS,considering the damage and strain rate effect of steel and concrete materials,the dynamic response under impact load is analyzed,and the failure behavior of frame structure components and connected steel joints under the impact load of upper falling layer is studied.The main contents are as follows:（1）Select a reasonable and correct material constitutive model,determine its mechanical properties,and establish a three-dimensional finite element model by using the general finite element software ABAQUS.By comparing with the test results in the existing literature,verify the effectiveness of the established constitutive model and the accuracy of the calculation results of the finite element model,and establish a prefabricated concrete frame structure model connected by new steel joints.（2）The parameters of prefabricated sub frame structure connected by steel joints are analyzed,and the effects of different impact load area,impact position and impact kinetic energy on the dynamic response and joint connection performance of frame structure are studied.By comparing and analyzing the data of impact force,beam mid span deflection,concrete damage,steel joint strain and the proportion of energy consumption of each component,the variation law is summarized.（3）The parameters of prefabricated frame structure connected by steel joints are analyzed,and the effects of axial compression ratio and surrounding constraints on the dynamic response and joint connection performance of frame structure are studied.Compared with the cast-in-situ concrete frame structure,this thesis analyzes the advantages and disadvantages of the prefabricated frame structure connected with new steel joints,summarizes its change law by comparing and analyzing the data of impact force,beam mid span deflection,concrete damage and steel joint strain,and explores the feasibility of changing or adding the connecting components of steel joints to enhance the connection performance of joints.The results show that the impact load area has a significant effect on the deformation of steel joints and concrete damage.When the impact position changes,the deformation of steel joints is smaller than that of beam and column members,and the damage range of beam and column members changes significantly.When the kinetic energy is the same,the greater the impact momentum is,the lower the peak value of impact force is,the longer the action time is,and the smaller the momentum is,the more prone to secondary impact.With the increase of kinetic energy,the damage degree of beam members increases,and the damage range is more concentrated.The vertical force of the column has an adverse effect on the deformation of the steel joint,but the effect is small,which has a beneficial effect on the concrete damage,and the effect is significant;Considering the influence of surrounding constraints,it has little influence on the deformation of steel joints.Compared with not considering surrounding constraints,the damage of concrete has no obvious change,the peak value of impact force is the same,but there is vibration fluctuation,the curve trend is consistent,the peak value of deflection in the middle of beam span increases,and the vibration amplitude decreases;Adding connecting steel plates at the connection between connecting bars and end plates and adding connecting steel plates between connecting end plates can effectively reduce the deformation of the connection of column embedded parts and improve the connection performance of steel joints,but the improvement effect on concrete damage is not obvious;Compared with the cast-in-situ concrete frame structure,the new steel joint connected frame structure reduces the damage degree and range of beam members,and the peak impact force and mid span deflection of beam are basically consistent with the cast-in-situ frame.