Study On Combination Behavior Of Arch Box Roof With Prefabrication And Cast-in-place Of Rigid Skeleton Concrete Arch Bridge

The rigid skeleton box concrete arch bridge is usually poured on the rigid skeleton of the closure arch by ring and segment,but the process is complex,the pouring time is long,and the concrete shrinkage and creep in the later stage are large.For this reason,the concrete of the bottom slab and the rigid skeleton of the arch box of Yutang super large bridge are prefabricated on site.The concrete of the top slab is partially prefabricated and partially cast-in-place.The prefabricated slab is used as the bottom formwork of the concrete of the top slab.After the bridge is completed,it is used as a part of the top slab of the arch box to participate in the stress.Therefore,a joint surface appears in the concrete of the top slab.Under the combined action of axial force and bending moment,the working performance of the joint surface will be directly related the mechanical behavior tied to the main arch ring.Therefore,based on Yutang super bridge,this paper studies the combination behavior between the prefabricated layer and the cast-in-place layer of the roof of the arch box of the rigid frame concrete arch bridge,and the main research contents are as follows:(1)Mechanical behavior analysis of solid web arch box of rigid frame arch bridge.Based on the theory of elasticity and the assumption of plane section,the internal force distribution formula of box section bottom plate,web plate and top plate under the condition of only axial force,only bending moment and simultaneously axial force and bending moment load is derived,and the design example is verified.(2)Analysis of the whole construction process of the rigid frame arch bridge with prefabricated bottom plate and partial top plate hoisting.The finite element software is used to establish two kinds of calculation models of different element types in the whole construction stage of Yutang super large bridge.In the two models,the rigid skeleton is simulated by spatial beam element,while the outer concrete is simulated by plate element or joint section in the construction stage.Analyze the cable force changes of the buckle cable and anchor cable during the construction process,the stress changes of the main steel pipe,the concrete in the pipe and the outsourcing concrete on each key section of the arch ring,the arch formation,the bridge formation line shape of the main arch and the elastic stability coefficient of each construction stage.(3)Local refined stress analysis of arch box roof of arch crown section and arch foot section of rigid skeleton concrete arch bridge.According to the results of the finite element simulation,the actual load on the roof is obtained by using the internal force distribution formula of the box section.Through the simplification of boundary conditions,the finite element model of precast and cast-in-place composite slab is established to analyze the stress and deformation state of roof precast layer,cast-in-place layer and connecting reinforcement under the actual load condition.(4)In order to analyze the influence of the reinforced structure of the interface between the roof prefabrication and the cast-in-place layer on the mechanical behavior,two kinds of reinforced structures of the interface between the roof prefabrication and the cast-in-place of the arch box are designed,i.e.adding the concrete tooth block and adding the L-shaped reinforcement.The refined analysis model is established by using the finite element software,and the lifting effect of two different ways on the overall cracking bearing capacity and ultimate bearing capacity of the combined plate component is compared,and the optimal technical guarantee measures for the combination of prefabrication and cast-in-place construction scheme of the roof are analyzed.