Experimental Study On Hollow Slab Beam Strengthened With Steel Cable Polyurethane Cement Composite

A large number of hollow slab girder bridges are used in high-grade highways in China.With the continuous increase of traffic volume and the increase of vehicle load,some old hollow slab girder bridges can not meet the requirements of normal use.There are cracks,whitening,corrosion of steel bars and other diseases at the bottom of the beam,and the bearing capacity can not meet the design requirements,which brings great security risks.As a new type of bridge reinforcement material,polyurethane cement composite has many outstanding advantages,such as low density,high strength,corrosion resistance,strong adhesion and fast hardening speed.Based on the science and technology plan(2017B97)of Shandong Provincial Department of transportation and the key research and development plan(2019GGX102041)of Shandong Province,indoor material test,structural model test and theoretical research are carried out in this paper.The mechanical properties of fiber-reinforced polyurethane cement composite and the bearing properties of hollow slab reinforced by steel wire rope polyurethane cement composite are studied.1.In order to enhance the mechanical strength and further improve the deformation ability of polyurethane cement composite.In this paper,the mechanical properties of carbon fiber,PVA fiber and steel fiber reinforced composite were tested by three-point test.The results show that the three kinds of fibers can improve the flexural properties of polyurethane cement composite.The best mixing ratio of carbon fiber and PVA fiber is 0.04%-0.05%,0.2%-0.3% respectively,and the best mixing ratio of steel fiber is1%.The strength and ductility of the composite are greatly improved.2.Through four test plate beams,one of them is not strengthened as the test comparison beam,two beams are respectively strengthened with 7 steel wire ropes,11 steel wire ropes and polyurethane cement composite materials,and one beam is damaged and then strengthened with 7 steel wire ropes and polyurethane cement composite materials.Through the load failure test,the failure mode of each hollow slab beam,the crack development law,and the peeling condition of the reinforcement layer and the beam body are obtained.Based on the analysis of the flexural rigidity,ductility and deflection of the test beam,the bearing capacity differences of different reinforcement methods and different damage degrees of the test beam are obtained.Through the analysis of the strain along the height of the test beam,all beams are in line with the plane section assumption,and the overall mechanical performance of the strengthened beam is good.3.Based on the summary of the failure mode of the strengthened beam,the calculation diagram of the hollow slab beam strengthened by steel wire rope polyurethane cement composite material is established,and the calculation formula of the bending capacity of the beam strengthened by this method is deduced.The formula can be used to evaluate the bearing capacity of strengthened beams.It lays a theoretical and experimental foundation for the reinforcement of hollow slab beams with steel cable polyurethane cement composite.