The Study Of Mechanical Properties Of Externally Prestressed Reinforced Railway Slab Culvert

The most culverts built 70-90 years of the early 20 th century is in the use. Although structural design load is low, various diseases of cover culverts,which have been unable to meet the growing requirements of heavy-duty are increasing.So it is important for the cover culvert structure reinforcement to achieve load highlight. As a simple way of structure reinforcement,externally prestressed structures can effectively improve the structure of inadequate bearing capacity and other issues, then it is widely used in engineering, and has been constant innovation in construction.Currently, the research of externally prestressed are mostly based unbonded prestressed research theory, on the background of the research results and the study of the disease Datong-Qinhuangdao line used externally prestressed reinforcement, and based on the pertinence of the external tendons stress increment, the beam midspan deflection and the concrete compression strain,and the boundedness of external prestressing slab culvert, the calculation model of linear type externally prestressed slab culvert structure in beam bottom is proposed, meanwhile,researchers analyse the stress increment of external prestressing sructure systematically with strain and deflection, the specifications are as follows:(1)The paper describes the current situation of the externally prestressed structure at home and abroad as well as the frequently-used methods of reinforced culverts,besides,it analyzes the respective reinforced principles and the advantages and disadvantages.( 2) Using the geometrical relationship before and after the structure deformation,a unified expression in uniform load,third point loads, concentrated loads for external tendons stress increment of externally prestressed slab culvert is solved in railway operation stage.Through the iterative calculation of section internal force balance equation,the numerical solution of the stress increment is received considering the influence on externally prestressed stress increment of anti moment. And sensitivity analyses are performed to study the parameters that affect the reinforcement effect.(3)Entity finite element model are established for culvert by MIDAS/FEA to analyse structural effects.The model agrees well with the theoretical value which meet the computational demands.( 4) The paper produced a 1: 1 Datong-Qinhuangdao railway culvert model used externally prestressed reinforcement with similar principles and a load test carried out in the laboratory under the normal stage.The test mostly measures the deflection,ordinary steel strain,concrete compressive strain, the externally prestressed stress increment.Compared before and after reinforcement, applying different effective prestressing, the concretecompressive strain, midspan deflection,steel strain,external tendons stress increment reduce greatly, and the reinforcing effect is relatively obvious.The test comparison shows that the this article calculated formula in good agreement with experimental values. Speaking in general,the approximate value will produce the larger error for smaller culvert.Thus,the external tendons stress increment calculation method for article’s culvert uses linear type external prestressing slab culvert in beam bottom without external prestressing tendons steering block has some versatility,and the paper suggests in future studies improved.