Research On Shear Strengthening Performance Of Old PC Hollow Slab Girder Bridge Ends In Service By Grouting Method

With the comprehensive development of China’s economy,the traffic volume continues to grow,the proportion of heavy traffic continues to increase,and the design load continues to improve.Nowadays,old standard bridges have experienced varying degrees of durability and structural diseases during service,such as bottom plate transverse joints and web plate oblique joints near the support points,which reduce the shear bearing capacity of the bridge.In order to ensure the safe operation of such bridges,maintenance and reinforcement are needed.In addition,in high-speed reconstruction and expansion projects,the proportion of existing hollow slab beam bridges is relatively large.If these bridges are dismantled and rebuilt,it will not only extend the construction period,increase costs,but also cause resource waste and even pollute the environment.Given how to improve the shear performance of existing PC hollow slab beam bridges,it is necessary to adopt reasonable reinforcement plans to effectively prevent the recurrence of such diseases.This article focuses on the study of the mechanical performance of the "beam end grouting method" for shear reinforcement of old PC hollow slab beams in service.It summarizes and analyzes the research results of experts and scholars on the shear reinforcement of old PC hollow slab beam bridges in service.On the basis of demonstrating the feasibility of the technology,Midas Civil and Abaqus finite element software are used to theoretically analyze the reinforcement performance and combined with scaled model test data analysis,Complete the research on the shear performance of the "beam end grouting method" to reinforce the old PC hollow slab beam bridge in service,and determine practical and feasible construction techniques.The main research work and conclusions are as follows:(1)We compared and analyzed the differences in vehicle loads,impact coefficients,and action combinations between the new and old specifications,and established a finite element model of the bridge according to the old design drawings.We calculated the shear effect of the existing and old specifications of the bridge under the theoretical normal use state and ultimate bearing capacity limit state under the current design specifications,providing basic data support for subsequent structural model tests and finite element analysis.(2)Each experimental beam undergoes four stages under load: elastic stage,elasticplastic stage,plastic failure stage,and unloading stage.By analyzing the load displacement curves of each experimental beam,it can be seen that the mid span deflection of the 1989 version of experimental beams L2 and L3 reinforced with end grouting decreased by 15% and 24% respectively compared to the unreinforced experimental beam L1,and the mid span deflection of the 2004 version of experimental beams L5 and L6 decreased by 19% and 27% respectively compared to the unreinforced experimental beam L4.It is clear that the stiffness of the prestressed hollow slab beam has been improved after reinforcement.(3)Under the same level of load,the main tensile strain value of the test beam at the same position significantly decreases compared to the strain value of the unreinforced beam.This indicates that the grouting body at the end of the test beam effectively participates in the overall stress process of the test beam,shares the shear stress during the stress process,and plays a good shear resistance role.Compared to the unreinforced test beam,the main tensile strain in the L2 web shear compression zone of the 1989 version test beam decreased by 32%,the main tensile strain in the L3 web of the test beam decreased by 40.5%,the main tensile strain in the L5 web shear compression zone of the2004 version test beam decreased by 46.3%,and the main tensile strain in the L6 web of the test beam decreased by 56.1%.After the reinforcement of the test beam,the shear bearing capacity was effectively improved.(4)Finite element simulation analysis was conducted on the stress process of the experimental beam,and the constitutive and contact relationships of the materials required in the modeling process were elaborated.The modeling process was detailed.The development trend and distribution of cracks in finite element analysis,as well as the deflection and load strain of the test beam,were compared and analyzed with the experimental results.The theoretical calculation results of the finite element model were in good agreement with the experimental data,verifying the rationality and reliability of the experimental results.