Experimental Study On Reinforcement Of Shear Connections In Precast Box-Beam Bridges

Precast concrete box-beams have been widely used in highway bridges.However,with the aging of the bridge,the wearing surfaces near shear connections have been found to be cracking damaged,which will lead to the weakening of bridge lateral connection ability and the overall bearing capacity of bridge structure,even the so-called “single-beam bearing”.Until now,there are little experimental research on reinforcement of shear connections at home and abroad.In this paper,the strengthening of shear connections by replacing damaged wearing surfaces with thick reinforced concrete pavement was experimentally studied.The failure modes and the ultimate bearing capacities of the specimens were obtained.By comparing with the maximum internal forces as derived from finite element analysis of whole bridge,the feasibility of the reinforcement scheme can be proved.First of all,this paper investigated and sumed up literatures concerned and analyzed the current status of the bridge,the failure characteristics of shear connections and the reinforcement scheme.Secondly,Midas/Civil model has been estabilshed based on the principle of lateral distribution calculation.The influence lines of shear connection at the middle of bridge have been extracted so that most unfavorable load combination has been got incorporation with a corresponding software for calculationg different combination of vehicle load,providing the basis of arrangement of vehicle load in full bridge model.Then,ABAQUS full bridge finite element model was established,considering the maximum load case and the maximum bending moment conditions of the vehicle load conditions.The ultimate bearing capacity analysis of the full-bridge solid model was carried out based on the JTDG60-2015 "Code for Common Design of Highway Bridges and Culverts",combining with the most unfavorable load combination.The internal force combinations of 600 mm wide-span hinges were extracted and the data comparison was provided for the test results;After that,three fullscale specimens each containing three box-beam segments and two shear connections were fabricated,and the static tests considering different load cases were conducted.The failure modes and the ultimate bearing capacities of the specimens were obtainedResults show that all specimens cracked originally at the bottom of shear connections and finally collapsed as bending failure or shearing failure of upper pavements.Better ductility of specimens was also observed.By comparing with the maximum internal forces as derived from finite element analysis of whole bridge,the flexural and shear bearing capacities of strengthened shear connections are higher,which indicates that the investigated strengthening method could be used in real applications.