Mechanical Behavior Of Steel-concrete Joint Section With No Cells And Rear Bearing Plates

As a key node in the hybrid beam structure,the steel-concrete joint section with no cells and rear bearing plates has a novel structure and complex stresses,and it is of great theoretical value and practical engineering significance to study its whole process force characteristics and transmission mechanism.In this paper,a negative moment scaling model test of the steel-concrete joint section with no cells and rear bearing plates and a refined finite element model were carried out to study the whole process of the joint section,the main analysis is on the force characteristics and transmission characteristics of the joint section under various load classes.On this basis,a parametric analysis of the key design parameters of the joint section components was carried out.The main conclusions are as follows.(1)According to the analysis of the 1:3 scaled-down model of the steel-concrete joint section with no cells and rear bearing plates,the specimen is in the elastic stage under the design load;under the overloading(2.32 times the design load)condition,the specimen enters the elastic-plastic stage,and the residual displacement ratio after unloading:18.97%;the stresses of the specimen under the design loading conditions are small,the joint section is reasonably designed,and the structure is safe and reliable.(2)Based on the ABAQUS finite element software,the friction contact model M1 with studs and the model M-2 without studs binding constraints were established and analysed respectively.The results show that the calculated results of model M-1 are more consistent with the test,and the studs modelling method should be used to study the local stresses in the joint section.(3)By combining the whole process of force finite element analysis of the joint section,the vertical deformation of the model is small under design load,2 times design load and yielding load,and there is no obvious bending angle;under peak load and damage load,most of the stud roots yield and the concrete beam section is damaged,resulting in a gradual decrease of the bearing capacity of the model,and the model force reaches the limit state.(4)Through the analysis of the transfer process of the joint section,the load is mainly transferred from the steel beam section to the bearing plate through the top and bottom of the steel beam section and the U-rib,and the load is dispersed to the joint section through the bearing plate and the welded stud shear joint;the steel top and bottom of the joint section and the studs jointly bear 41%of the internal force and the concrete bears 59%;as it moves away from the bearing plate,the load is gradually transferred from the steel beam to the concrete through the shear joint and the friction between the steel and the concrete.The load is gradually transferred from the steel beam to the concrete through the shear joint and the friction between the steel and concrete,with the concrete bearing 93.2%of the internal force.(5)The effects of changes in the thickness of the steel top and bottom plates,the thickness of the bearing plate,the prestressing load and the spacing of the studs on the force performance of the joint section were analysed.The results show that:increasing the thickness of the steel top base plate can make the load transferred to the bearing plate more uniformly,and the recommended thickness is 18-22 mm;If the thickness of the bearing plate is too large,it is not conducive to the vertical transfer of load in the joint section,and the recommended thickness is 54-70 mm;appropriate increase in prestressing load can effectively control the separation of concrete and bearing plate,peg pull-out and other phenomena;Increasing the spacing between studs increases the efficiency of force transfer in the joint section.