Study On Reinforced Concrete T-beams Strengthened With A Composite Of Prestressed Steel Wire Ropes Embedded In Polyurethane Cement(PSWR-PUC)

With the application of prestressed steel wire ropes(PSWR)in the bridge reinforcement projects,the mortar or the composite mortar as a material for steel wire ropes embedding exposed the defects in the practices,such as low intensity,cracking easily,fall off,and influencing the durability of steel wire ropes.Polyurethane cement(PUC)material,as a kind of polymer concrete material,has the characteristics of light weight,high strength,high toughness,good adhesiveness and corrosion resistance.In this paper,polyurethane cement is used as the embedded material of steel wire ropes to form an innovative technique,namely,a composite of prestressed steel wire ropes(PSWRs)embedded in polyurethane cement(PSWR-PUC).Light and high strength polyurethane cement material can not only anchor prestressed steel wire ropes,but also passively participate in structural stress.The problems embodied in mortar or composite mortar can be solved.This paper is based on the key science and technology project "Study on Bridges Strengthened with a Composite of Prestressed Steel Wire Ropes Embedded in Polyurethane Cement" supported by Jilin Provincial Transportation Department(No.20150107).the mechanical properties of polyurethane cement were firstly measured,based on the static load tests,fatigue tests and numerical analysis of the PSWR-strengthened beams and the PSWR-PUC-strengthened beams,field tests of two actual bridges were carried out before and after reinforcement.The research content and innovation results of this paper are as follows:1?The properties of polyurethane cement with a density of 1550kg/m3(PUC-1550)were studied.The compressive,flexural and axial tensile strength of the material were obtained by experiments,and the stress-strain curve relation was fitted.The bonding strength and failure modes between polyurethane cement and concrete under two test conditions were obtained by axial tensile bond tests and bending bond tests.The effect of ambient temperature on mechanical properties of materials was analyzed,through the axial tensile tests between-40 degrees and 60 degrees.The determination of corrosion resistance to acid and alkali indicated that polyurethane cement has good chemical corrosion resistance.2?The flexural reinforcement test of sixteen pieces of T-beams strengthened with a composite of prestressed steel wire ropes embedded in polyurethane cement(PSWR-PUC)was studied(One unstrengthened beam,four PSWR-strengthened beams and eleven PSWR-PUC strengthened beams).The material into which the wire rope was embedded,the prestressed wire rope anchorage form,the polyurethane cement material thickness,the number of wire ropes,the prestress of wire ropes,loading method and the load reinforcement were taken as variables.The experimental results:Compared with the PSWR reinforcement,the PSWR-PUC can significantly increase the yield load and ultimate load of the reinforced beams;the limited crack expansion capacity of PSWR-PUC reinforcement is better than that of PSWR reinforcement,especially after the main girder steel yield;the strength,crack limiting capacity and rigidity of the reinforced beams increase with the increase of the thickness of PUC,and decrease with the decrease of the prestress of the steel wire ropes.3?Numerical simulation of beams strengthened with PSWR-PUC is carried out The influence of concrete strength and reinforcement ratio on the flexural behavior of reinforced members is analyzed.The results show that the simulation results agree well with the experimental data;The yield load of reinforced member increases slightly with the increase of concrete strength,and the yield deflection value is very close;the ultimate bearing capacity of beams increased with the increase of reinforcement ratio when the reinforced layer broke.4?The flexural fatigue test of eight pieces of T-beams strengthened with PSWR-PUC was carried out.The effects of PSWR-PUC reinforcement and PSWR reinforcement on structural fatigue performance were compared,and the fatigue failure mechanism of PSWR-PUC reinforcement was analyzed.The experimental results:Compared with the PSWR reinforcement,the PSWR-PUC reinforcement significantly improved the stress distribution of flexural member,and reduced the reinforcement stress,so as to greatly improve the fatigue life of the structure;The fatigue performance of flexural members reinforced with PSWR-PUC is not completely dependent on the stress amplitude of the steel bars,but also affected by the prestress of the steel wire ropes and the stress amplitude of PUC.5?According to the simplified constitutive relation of materials,the whole process of flexural reinforcement is analyzed,including the nonlinear analysis of rectangular section and T-shaped section.The calculation methods of flexural reinforcement are studied,and the calculation formulas of cracking load,ultimate bearing capacity,deflection and crack are proposed.6?The reinforcement work of two similar bridges in Heihe and Jixi,heilongjiang province was completed,using PSWR-PUC reinforcement and PSWR reinforcement respectively.The loading tests were carried out before and after reinforcement,and the validity of reinforcement method is verified by collecting the parameter information of strain and deflection before and after reinforcement.