| With the rapid development of transportation and the continuous increase in traffic volume and load levels,the demand for bridge reinforcement is increasing.Compared with traditional reinforcement methods,the advantages of new materials and new technology to strengthen the bridge have attracted more attention.This article describes a new type of active reinforcement method,polyurethane cement wire rope reinforcement.In order to verify the feasibility of this reinforcement method,bending test was used to test unreinforced beams that are subject to different reinforcement schemes.By comparing the test data of each test beams,the reinforcement effect of polyurethane cement wire rope was analyzed.Strength,stiffness and carrying capacity are studied in a case study,before and after reinforcement.The reinforcement effect of polyurethane cement wire ropes were compared and analyzed.Firstly,the strengthening mechanism and advantages of polyurethane concrete steel wire ropes are introduced.The mathematics of calculating prestress loss,resistance,deflection and stress at the top and bottom of the cross section is derived.The non-linear factors involved in the bending test are considered,and the constitute model that illustrates the stress-strain relationships of concrete,polyurethane cement,ordinary steel bars,and pre-stressed steel wire ropes were deduced.Secondly,the mechanical property test of concrete,polyurethane cement,ordinary rebar and pre-stressed steel wire ropes were carried out to ensure that they met experimental requirements.The reinforcement scheme and manufacturing technology of polyurethane cement steel wire rope are introduced.T-beams that are of three meters in length were used in the bending reinforcing experiments.Steel wire ropes and polyurethane-concrete composite steel wire ropes were respectively used.The testing specimens consisting of 5 test beams:a control beam that was not reinforced;a beam strengthened with 5 steel wire ropes alone;and beams strengthened with polyurethane cement along with 3,5 and 7 steel wire ropes,respectively.Flexural test was conducted on each test beam.By comparing the test data,the reinforcement effect of polyurethane cement wire rope was analyzed.Then,a finite element analysis was conducted using software Midas/FEA.Finite element model was constructed for each test scenario:unreinforced beam,beam strengthened with 5 steel wire ropes exclusively,and polyurethane cement strengthened beams with 1,3,5,and 7 steel wire ropes respectively.At the same time,the ultimate bearing capacity of each test beam was calculated theoretically.By comparing theoretical calculation results,Midas/FEA calculation results and experimental results,accuracy of the test results and the reliability of the calculation theory can be verified.Finally,based on a case study of the polyurethane cement wire rope strengthened Jiayinhe Bridge,static load tests were conducted before and after reinforcement.The experimental data such as stiffness,strength and bearing capacity of polyurethane cement steel wire rope reinforcing method were analyzed hence providing insights for future reinforcement projects. |
