Research On Load Transfer Mechanism And Design Method Of Steel-Concrete Joint Of Hybrid Box Girder Bridge

This paper was based on the background of Shanxi Weihe Grand Bridge.To investigate the mechanical behavior,load transfer mechanism and design method of steel-concrete joint(SCJ)of continuous beam Bridge,works of domestic and foreign scholars were summarized,model test and finite element analysis were carried out,and formulas were derived.The main research results are as follows.A fourteen meters long segment model test of Weihe Grand Bridge with a scale of 1:2 was carried out.Deflection,Stress of key sections and steel-concrete slip of the model were measured under three load conditions.The results show that the structure was elastic under serviceability limit state condition.The steel-concrete slip is small and no more than 10.7?m.when the load came up to 0.8 times of the design load of ultimate limit state condition,the concrete cracked at the two sides of the bottom deck,and along with the increasing of the load,cracks developed.No steel plate buckled,no weld broke,concrete and steel of SCJ weren't separated during the entire process.Test results matched well with FEA results.Mechanical behavior and bending moment transfer mechanism of SCJ was analyzed by two finite element models.The results show that axial compressive force of top deck caused by bending moment and prestress is transferred from concrete to steel box by in-plane bearing of perfobond ribs' ends,shear connectors and out-plane bearing of bearing plate.Bearing plate serves as the main load-transferring component which transfers 69.8 percent axial load,shear connectors and perfobond ribs' ends transfers 15.6 percent and 14.6 percent axial load.The effect of in-plane bearing of perfobond ribs' ends cannot be neglected.The bottom deck of SCJ is under Axial compressive force because of prestress,but not all of the cross section is under compressive stress and some PBL connectors worked as resistance of the separation of concrete and steel.The design method of SCJ was studied in the end,the force distribution of PBL connectors was analyzed by using continuous springs to replace PBL connectors and the shear force formula of PBL connectors was derived.The results of formula and FEA matched well,the formula has good accuracy.The research results can serve as a reference for future study and design of similar structures.