Experimental Study On Flexural Behaviors Of Prestressed Reactive Powder Concrete Box Girders

Reactive Powder Concrete(RPC), one of ultra-high performance concrete, has a good application prospect, which has characteristics of high strength, high durability and high toughness, etc. At present, scholars at home and abroad had done a lot of research about the mechanical behavior of RPC beam. But most of them were about T beam and rectangular section beam, the study about box girder was little. And there were not covered the influence of transverse prestressing force to its bending performance. Based on, the bending tests of two prestressed RPC box girders were carried out. The Flexural behavior of RPC box girder and the influence of transverse prestressing force to its bending performance was studied through the tests. The main content of this paper includes the following sections.According to the test results, the prestressed RPC box girder displayed a good deformation capacity, with a maximal deflection of 1/50 of its span. The crack width and the short-time stiffness of the girder can be calculated according to the formula in Technical specification for fiber reinforced concrete structures( CECS 38:2004), with a coefficient of 0.4 and 0.2 considering influence from steel fiber, respectively. In the tests, the transverse prestressing force in the roof of RPC box girder had little influence on the flexural behavior, but the force could make a more uniform strain distribution of the compressive concrete so as to reduce the shear-lag effect and increase the ductility of the structure. By applying a transverse prestressing force of 2.95MPa(only 3.1% of the RPC prism compressive strength of 94 MPa) in the roof, the effective distribution width of box girder increased by 10%, and ductility index of structure increased by 3%. The formula to evaluate the cracking moment and the ultimate moment of a prestressed RPC box girder was proposed and verified by the experimental results.And a full range nonlinear program of prestressed RPC box girder for loading and unloading was developed. By validation, the nonlinear program is reliable. And the parametric study of the loading behavior was conducted. The results show that prestressed reinforcement ratio had influence on the cracking moment, ultimate bearing capacity and ductility, and the ductility performance was influnced by compressive strength and compressive ultimate strain of RPC, tension coefficient and reinforcement ratio of compressive zone.By using finite element analysis software ABAQUS,numerical simulations of the prestressed RPC box girder were conducted, the numerical results and experimental results were compared, meanwhile, finite element analysis of RPC box girder with the transverse prestressing force in the roof. The results show that the transverse prestressing force in the roof could make the normal stress of box girder roof reduc e, and reduced the shear-lag effect and made the strain distribution of the compressive concrete more uniform.