Study On Fatigue Behavior Of Subjected To Stud Corrosion Steel-Concrete Composite Beams

Under the action of repeated vehicle loads,the composite beam interface of the steelconcrete composite beam will produce relative slippage,which will make the interface staggered,causing rainwater and chloride ions and other substances to enter the stud position along the interface,resulting in corrosion of the stud and further.Deterioration of the durability of composite beams.In order to ensure the safe operation of steel-concrete composite girder bridges,the fatigue performance of composite girder after stud corrosion is studied in this paper.The main contents are as follows:(1)In this paper,8 steel-concrete composite beam specimens were made.Based on the artificial electrochemical accelerated corrosion test,composite beam specimens with different stud corrosion rates were obtained.The corrosion of the composite beam was observed,the crack width and length were measured,and the crack development diagram was drawn.It was found that with the increase of the corrosion rate,a longitudinal crack was gradually formed at the bolt position of the composite beam and increased accordingly.In this paper,8 steel-concrete composite beam specimens were made.(2)Based on the static test of the uncorroded member,the ultimate bearing capacity is obtained to provide the basis for the loading of the fatigue test.Then,fatigue tests were carried out on 7 composite beams with different corrosion rates,and their failure modes were obtained.The failure modes of the specimens showed that the bolts were sheared,the concrete was crushed,and the steel beams were broken.The reason for the change of the failure mode was:With the increase of the corrosion degree of nails and interface and the increase of fatigue loading times,the shear connection degree of the composite beam changes gradually.(3)Based on the fatigue test of composite beams,it is analyzed that with the increase of fatigue loading times,the components of composite beams produce cumulative damage,resulting in irrecoverable residual deformation.The residual slip and residual deflection of the composite beam both increased,and the residual deformation increased rapidly at the initial stage of loading,and then entered a stable development stage,and the residual deflection and residual slip showed an "S"-shaped law.When the fatigue failure finally occurs,the residual strain of the mid-span composite beam shows a decreasing trend with the increase of the corrosion rate.(4)Based on the fact that the stiffness degradation of composite beams is the external manifestation of fatigue damage,the fatigue damage amount of composite beam stiffness degradation is defined,and the parameters of each fatigue failure test beam are fitted to reveal the stiffness degradation of composite beams during the fatigue test process.The "S"-shaped law is obtained,which correlates the function of corrosion rate and comparative stiffness,and establishes a calculation model for the stiffness degradation law of corrosion rate of steelconcrete composite beams and studs.The experimental values in this paper are in good agreement with the calculated values of the fatigue stiffness model.Accuracy and plausibility of degradation computational models.