Research On Widening Technology Of Concrete Continuous Box Girder Bridge Based On Transverse Stiffening Steel Plate

The existence of transverse prestressing tendons makes it difficult to widen the splicing of threedimensional prestressed concrete box girder bridges by traditional methods in the expressway expansion project.Based on the widening project of the Yanhe Bridge on Huaijiang Expressway,this paper puts forward a new transverse splicing scheme using transverse stiffening steel plate.By embedding the transverse stiffening steel plate longitudinally on both sides of flange of the new and old bridge,the new and old bridge box girders can be connected.In order to study the reliability of this technology,the solid finite element model of the whole bridge is established by using Midas FEA.Based on that,the local model is established by using sub-modeling method.The load conditions considered in the analysis include the difference of shrinkage and creep of the new and old box girder,the foundation settlement difference,the live load and load combinations.The results show that under various load conditions,the mechanical performance of this structure is well.This splicing scheme of transverse stiffened steel plate can better coordinate the deformation between the old and new bridges.The longitudinal shrinkage of the new bridge will also lead to transverse displacement.Under the influence of foundation settlement,the vertical deflection of new and old box girders changes smoothly.Using the sub-model method,a local finite element model is established.By extracting the load conditions and displacement conditions of the original model,the boundary conditions are applied to the sub-model.By analyzing the stress trajectory of the box girder flange and the steel plate,the force transmission mechanism of the transverse stiffened steel plate under the action of vehicle load,foundation settlement difference and concrete longitudinal shrinkage and creep is studied.By establishing the interface unit between concrete and steel plate,the shear stress and surface tensile stress of the interface are studied and analyzed.The results show that the interface stress generated by vehicle load is small,but the influence of the foundation settlement difference and the shrinkage and creep of box girder lead to stress concentration at the end of the concrete flange of the key section.The interface stress may cause partial cracking of the structure.Finally,the sensitivity analysis of the related dimension parameters of the splicing structure is carried out,and the influence of the thickness and height of transverse stiffened steel plate,the layout spacing,and the joint width between the old and new box girders is studied.The analysis shows that the change of dimension of steel plate has little influence on the new and old box girder and splicing effect,but has a greater impact on the stress of the transverse splicing steel plate itself.Based on that,the optimum values of dimension parameters are given.