Research On Transverse Splicing Structure For Extended Long-Connected Concrete Bridges

In the highway expansion project,the mainstream bridge expansion plan adopts the transverse splicing method of keeping the superstructure connected while the substructure seperated.However,the interaction between the old and new bridges due to time-dependent effects will cause constraint stress in the new and old structures,even cause extrusion failure of the anti-seismic block due to the large lateral deflection at beam end section.As the bridge span increases,this effect becomes more significant,which poses a huge challenge to the success of the horizontal splicing of long-span continuous beam bridge.In order to solve the problems above,this paper mainly conducts an in-depth study on a new type of horizontal splicing structure of concrete continuous box girder bridge based on corrugated steel plate,and try to explore its feasibility,mechanical properties and force transmission mechanism so as to provide theoretical reference for similar bridge widening practice.Based on the Yan Shao River Bridge widening project of Huaijiang expressway,comparative analysis of two horizontal splicing structures were conducted in this paper.The traditional practice of widening the box girder bridge is to pour concrete and implant steel bars for articulation,while a new horizontal splicing structure is proposed by using the corrugated steel plate to absorb and dissipate the differential longitudinal shrinkage deformation of the old and new bridges.The finite element models of full-bridge structure before and after widening by different splicing methods were established by Midas FEA,and the transverse stress and deformation state of the widened structure especially the splicing site is systematically analyzed in this paper,under the action of the shrinkage and creep difference of the new and old bridges,the settlement of the new bridge and the live load.Then the structural size of the steel plate is adjusted to control the stiffness of the horizontal splicing structure,to study the influence on the stress and deformation state of the cantilever plate of the new and old bridges before and after widening,so as to obtain a better horizontal splicing effect.Results show that transverse splicing of the new and old bridges will mainly have a relatively large impact on the roof plate of the old bridge,in particular,the inner flange plate of the old bridge beam end section has the largest tensile stress increase.Among them,the difference between the shrinkage and creep of the new and old box girder and foundation settlement difference are the most important factors affecting the long-term stress characteristics of the widened concrete bridge.When the traditional joint splicing is used,the transverse stress of the inner flange plate of the old bridge reaches 4.557 MPa under the most unfavorable load,which is far beyond the tensile strength of C50 concrete.Most areas have obvious cracking possibility and need to be effectively reinforced.While the maximum tensile stress on the inner flange plate of the old bridge is 2.510 MPa,which is within the safe range when the corrugated steel plate is used for splicing.At the same time,the research results show that the use of corrugated steel plate splicing can effectively solve the problem of large lateral deflection at beam end section,which can adapt to the widening requirements of larger span concrete continuous box girder bridge,and the splicing waiting time can be shortened.Therefore,the comprehensive mechanical properties of the corrugated steel plate splicing structure are superior to the traditional hinged splicing structure.And a better combination scheme of the splicing structure parameters of the corrugated steel plate is established by investigating the influence of the structural parameters of the new splicing structure on the widening structure.