Effect Of Stud Corrosion On Mechanical Properties Of Steel-concrete Composite Beams In Negative Bending Moment Region

The durability of steel-concrete composite beams is an important aspect affecting the longterm operation of long-span bridges.The mechanical properties of steel-concrete composite beams in the negative bending moment area affected by stud corrosion in coastal salt-spray environment are particularly worthy of attention.There are few studies on stud corrosion.In order to study the influence of stud corrosion on the mechanical properties of steel-concrete composite beams in the negative bending moment region,the main work and conclusions in this thesis are as follows:(1)The push-out test was carried out according to the design standards EC4.The studs were corroded by the constant current accelerated corrosion method and then the vertical static load was applied on the push-out test specimens.The ultimate shear capacity,load-deflection curve,vertical strain distribution of the specimen and the degradation mechanism of the stud corrosion shear capacity were obtained.The results show that the age of early-strength concrete has no obvious effect on the shear capacity and the low-shrinkage performance ensures that the concrete does not appear rust expansion cracks.The corrosion of studs leads to the decrease of shear capacity,but when the cross-section loss factor is not considered,the shear capacity increases slightly first and then decreases linearly with the corrosion.The standard formula needs to be modified by the corrosion reduction factor λ,and the shear stiffness also decreases with the increase of corrosion rate.The vertical strain of push-out specimens is compressive strain,and the maximum value appears near the stud.(2)The tests of steel-concrete composite beams corroded by shear studs were carried out.The studs were corroded by constant current accelerated corrosion method and the negative moment load was applied by two-point symmetrical loading.The load-interface relative slip relationship,load-mid-span deflection relationship and load-mid-span strain distribution relationship in the elastic stage of the specimens were obtained.The results show that there is no obvious relationship between the bending bearing capacity of the negative moment zone and the corrosion rate of the studs.Under the same load in the elastic stage,when the corrosion rate of studs increased,the cracking of composite beams is advanced,the interface slip increases in line,the bending stiffness decreases,and the mid-span deflection increases.The greater the corrosion rate of the stud,the earlier the specimen enters the plastic stage and the earlier the failure occurs.The elastic section of the mid-span section before and after cracking satisfies the plane section assumption.Under the same load,the position of the neutral axis moves up with the increase of the corrosion rate of the studs,and the upward speed of the neutral axis also accelerates.(3)The composite beam model consistent with the test was established by numerical simulation,and the numerical simulation results were consistent with the test results.According to the results,the bending stiffness and longitudinal shear stiffness of the composite beam decreased with the increase of stud corrosion.It is feasible to simulate the stud by solid element,and the radial displacement of the stud can accurately simulate the corrosion and expansion of the stud.