Study On Mechanical Properties And Structural Analysis Of Ultra High-performance Concrete (UHPC) Pipes

Concrete pipe is one of the more widely used pipes in water supply and drainage engineering.The ultra high-performance concrete(UHPC)has higher tensile,compressive strength,compactness and durability than ordinary steel fiber reinforced concrete.The application of UHPC into the water supply and drainage pipeline can effectively improve the performance of the pipe structure and prolong the service life of the pipeline.In this paper,the mechanical performance of UHPC was studied at the start,then the structural performance of pipes prepared with UHPC was studied by means of experimental and theoretical analysis.The main work of this paper is as follows:(1)The UHPC prepared had obvious strain hardening characteristics under uniaxial tension,and the compressive strength was above 150 MPa.Through the uniaxial tensile test of prefabricated notched specimens,the relationship of stress and crack opening width of UHPC was obtained by DIC test.The addition of steel fiber significantly reduced the early shrinkage deformation of UHPC.When the steel fiber content reached more than 2%,the dry shrinkage strain did not decrease with the increase of steel fiber content.(2)Through the three-edge bearing test of UHPC pipe,it was found that the load carrying capacity and the top deflection of the reinforced UHPC pipe were 3.2 times and 3.5 times higher than these of the uninforced UHPC pipe,respectively.In the same grade and inner diameter concrete pipe,the wall thickness of the tube was obviously lower than that of the ordinary reinforced concrete pipe.The unreinforced UHPC pipe had four main cracks.The reinforced UHPC pipe exhibits multiple cracks and the number of cracks was large and the distribution was dense.(3)The ultimate load of the unreinforced UHPC tube was slightly higher than the crack load,and the ultimate load of the reinforced tube was 1.32 times higher than the crack load.The stiffness of two kinds of the tube were 30.2% and 29.46% of the elastic stiffness,respectively,when the tube reached the crack load,the stiffness of cracked tube did not decrease,and the top deflection of pipe and the top strain on the outer wall of pipe maintained a good linear relationship with load.(4)According to the UHPC tensile relation and section equilibrium,the relation of crack opening angle and bending moment was calculated.the crack load,ultimate bearing capacity,deflection of the crown of pipe and the load calculated value wass close to the experimental values.