Research On Seismic Performance Of Prefabricated Steel Reinforced Concrete Composite Column Base Joints

With the development of construction industrialization,prefabricated structure is widely used in the field of construction,which is in line with the development direction of industrial production.The problem of assembled steel-concrete composite structure is one of the most important and difficult problems to be solved in the seismic field of assembled structure at present.Therefore,this paper proposes a new type of dry-connection mode of precast SRC composite column base joint,which does not need to assemble reinforcement and pour concrete at the later stage of the connection module,so as to reduce the construction cost.The main research work and achievements are as follows:(1)In order to study the seismic performance of prefabricated steel-reinforced concrete composite column base joints,three new specimens with different shear span ratios were subjected to pseudo-static tests,analyzes the testing process of new type of column base joint specimens and the failure pattern,hysteresis curves and skeleton curve,ductility and energy dissipation,stiffness and strength,the results showed that:The hysteresis curves of the composite column base joint were full and shuttle shaped.They have excellent capacity for energy dissipation,strong resistance to plastic deformation,stable stiffness and strength degradation performance.The composite column base joints have good ductile deformation capacity,bearing capacity and superior seismic performance.(2)The constitutive relationship of the material and modeling process were deeply explored,and the refined finite element models corresponding to the test joints model were established respectively through ABAQUS.The result express:The results of finite element analysis well coincide with the experimental results,and the failure mode was similar,and the relative error of bearing capacity was small,which indicates that the results of finite element analysis can correctly reflect the stress state of the component,and the reliability of the finite element model were verified(3)Based on the test,the shear span ratio,the thickness of stiffening plate,the thickness of cover plate and,and the width-thickness ratio of square steel tube in the connecte module were taken as parameter variables.The finite element models(SPCZ-1～SPCZ-17)with corresponding parameters were established through ABAQUS,and they were loaded monotonically and reciprocally.The stress distribution under monotonic loading was clarified,and the influence of various parameters on the seismic performance of composite column base joints was summarized.The results show that the main failure of composite column base joint specimens under monotonic and reciprocating loading occurs in the connecting module.The decrease of shear span ratio,the increase of stiffener plate thickness and the increase of cover plate thickness can increase the plastic deformation capacity of the structure,which was beneficial to improve the failure mode of the connecting module.The increase of the width of the square steel tube will improve the stability and shear deformation ability of the connecting module,but the width of the square steel tube should be set within a reasonable range to avoid the adverse influence on the surrounding bolts.(4)Under the reversed cyclic loading,when the axial compression ratio was 0.3,with the increase of the shear span ratio,the overall deformation of the specimen increased,and the bearing capacity and energy consumption capacity decreased.The average decrease of the bearing capacity was 14.59%,and the average decrease of the energy consumption was 27.75%.At the same shear span ratio of stiffening plate thickness,with the increase of stiffener plate thickness,cover plate thickness and the width-thickness ratio of square steel tube,the bearing capacity and energy dissipation capacity of the new type column base joints can be effectively improved.The average increase of bearing capacity of stiffener plate thickness and cover plate thickness is4.86% and 9.85% respectively.When the width-thickness ratio of square steel tube was17 and 18,the bearing capacity is increased by 9.0% on average.The average increase of cumulative energy consumption was 20.41% with the increase of slab thickness.The results show that the cumulative energy consumption of 14 mm and 16 mm stiffeners was almost the same.The average increase of cumulative energy consumption value is32.67% when the width-thickness ratio of square steel tube increases.The stiffness degradation of all specimens was fast before yielding,and tends to be stable after yielding.The research results are of great significance for improving the connection form of the joint area of the column base connection of the assembled steel-reinforced concrete composite structure.