The Research On Static Behavior Of Wet Joint In New Steel-UHPC Composite Bridge Deck Under Negative Moment

The composite bridge deck structure formed by ultra-high performance concrete and steel deck has the advantages of high bearing capacity and good crack resistance.In practical engineering,segmental precast and assembly technology is often used in steel-UHPC composite bridge deck structure,and the precast UHPC layer of the segments is connected as a whole by wet joints.In order to explore the new structural form and optimize the wet joint structure,based on a bridge project,taking the wet joint of the new steel-UHPC composite bridge deck as the research object,the research work was carried out in the following aspects:(1)Full-scale model experiment of new steel-UHPC composite bridge deck was carried out.According to the UHPC mixture ratio developed by the project team,the material performance test was carried out;Based on the design scheme of bridge deck,the full-scale model specimen is designed and manufactured.The four-point bending static experiment of full-scale model specimen under negative moment was carried out,and the variation rules of crack development,failure pattern,mid-span deflection and strain of each measuring point with load were studied,the plane section assumption was verified,and the longitudinal relative slip law between steel and UHPC was revealed.(2)The finite element model of the full-scale model specimen was established.The plastic damage model,double broken line model and cohesive model were used to simulate UHPC,steel and wet joints respectively,and the contact between steel plate and UHPC was set as tie constraints.The finite element model which was consistent with the experiment results was obtained by trial calculation,and the load-displacement curve,load-strain curve and crack development of the model were compared with the experiment results.The results show that the finite element model had good accuracy.(3)The finite element parameter analysis was carried out.According to the theory of orthogonal experimental design,nine independent finite element models were generated by arranging and combining different parameter levels of the finite element model,and through the analysis of range and variance of the calculation results,the effects of various parameters on cracking,yield and ultimate load were revealed.The parameter that has the greatest influence on the cracking load is the steel plate thickness,and the diameter of the top longitudinal bar is linearly related to yield and ultimate load.The effect of UHPC wet joint length on the above three loads is not significant.(4)Based on the finite element parameter analysis,the optimal parameter combination was selected as the optimal design scheme.The parameter analysis showed that the increase of yield load is greater than that of cracking and ultimate load when the length of wet joint of UHPC is 1.2m.When the diameter of longitudinal bar at the top layer is Φ22,it is benefit to the cracking load.When the thickness of steel plate increases to 10mm,the cracking load can be increased.As far as this paper is concerned,the optimal parameter combination is UHPC wet joint length 1.2m+top longitudinal bar diameter Φ22+steel plate thickness 10mm.