Study On The Influence Of The Construction Schemes Of Cast-in-place STC Bridge Deck Pavement On The Finished Dead State Of Suspension Bridge

As a flexible structural bridge,under the action of natural factors such as vehicle load,temperature change,wind load,earthquake and moisture corrosion,the stress and deformation of a long-span suspension bridge are complex.It is easy to appear two major diseases,the damage of steel deck pavement and the fatigue cracking of steel deck structure.In order to improve the safety and durability of the bridge structure,the super toughness concrete(STC)steel deck pavement is intended for use in long-span suspension bridges.In general,we can only choose block placement as the construction schemes of the bridge deck pavement because of the large area of the long span suspension bridge.However,unlike the asphalt pavements commonly used in the past,the first-placed pavement layer will increase the bending stiffness of the stiffened beam structure because of the high modulus of elasticity of STC.Therefore,the batch pouring of STC is equivalent to the vertical stratification and vertical section construction of the beam structure,which means the staged formation of beam stiffness.When blocks are cast in place without counterweight measures,the strength of each block of STC will gradually increase the stiffness of the steel deck,forming the composite structure with steel deck and bearing load together,resulting in the stress state of the structure change in the hardening process of STC.The redistribution of internal force in this construction process will influence the realization of the design of suspension bridge.In order to study the influence of construction schemes of cast-in-place STC rigid pavement on the finished dead state of suspension bridge and select the reasonable cast-in-place construction schemes,the paper has summarized the domestic and foreign research results about pavement structure,mechanical properties,materials,and construction techniques of steel bridge deck.The following work has been done for single-deck and double-deck bridge suspension bridge.(1)Based on the nonlinear theory,the influence of construction schemes of STC pavement on the finished dead state of suspension bridge has been analyzed.The cast-in-place calculation simulation method of STC has been proposed,including the acquisition of stiffened beam shape(initial state of cast-in-place construction)and simulation of STC's stiffness variation.The establishment and simplification of the finite element model have been clearly defined and equivalent simplification validation has been completed.According to the internal force analysis of STC completed bridge operation,the STC construction internal force control standard has been put forward.(2)Taking a single deck steel truss stiffening girder suspension bridge--Hangrui Expressway Dongting Lake Bridge as the engineering background,the finite element model for the construction calculation of STC pavement has been established by ANSYS.The influence of different construction schemes on the main girder alignment and the STC internal force has been analyzed,and the optimal cast-in-place construction scheme has been proposed.Based on the same form of span,main cable area,etc.,a calculation model of steel box stiffened beam suspension bridge has been established.The influence of STC pavement on the internal force and main girder alignment of the bridge structure has been analyzed and influence rule of rigidity change of stiffened beam has been determined.(3)Taking a double deck bridge with three towers and four span steel truss stiffened beam suspension bridge as the engineering background,the finite element model for the construction calculation of STC pavement has been established by ANSYS.Through the analysis of the influence of different pouring schemes on the main girder alignment and the STC internal force,the rational pouring sequence,blocking principle and counterweight scheme of STC for multi-span continuous double deck bridge has been determined.(4)Taking three suspension bridges with large difference of stiffness discussed above as the objects for study,and based on the pouring sequence of pre-cast compressive region and post-cast tensile region for STC,the influence of the STC stiffness calculation method on the final stress during the construction process has been analyzed and a simplified method for the simulation calculation of the STC construction process has been proposed.Through the analysis of this paper,it shows that,for long-span suspension bridges,the impact of the different block principle,pouring sequences,and counterweight schemes used in the cast-in-situ construction of the STC pavement on the formation of the bridge is generally small,and does not change with the significant increase of "the ratio of STC and stiffening girder".However,the block principle,pouring sequence and counterweight scheme have a decisive influence on the internal force of the STC.The rules of cast-in-place scheme for STC pavement should be based on the general principles of the pre-cast compressive region and the post-cast tensile region,and the size of the post-cast section should be set up reasonably.Meanwhile,in order to reduce the tensile stress of STC in the finished dead state effectively,proper counterweight schemes should be applied before the STC in tensile region has been poured,grasping the position and the right moment of counterweight more precisely.For the finite element simulation of STC construction process,the calculation methods of STC stiffness will have an impact on the calculation of its internal force.It is more reasonable and convenient to adopt the method proposed in this paper that we can ignore the stiffness of STC outside the stress control region.