Experimental and theoretical study on flexural performance of concrete beams strengthened by unbonded prestressed ultra-high performance concrete layer.

Ultra High Performance Concrete (UHPC) has the advantages of high strength and good durability. The new technology of unbonded prestressed UHPC to strengthen ordinary concrete beams can give full play to the performance of prestressed "high efficiency" and UHPC "light durability". In this paper, through the test and theoretical analysis of 10 unbonded prestressed UHPC reinforced beams, the bearing capacity of prestressed UHPC reinforced beams and the key parameters affecting the flexural performance (i.e., UHPC strength, thickness, prestressed tensile degree and prestressed reinforcement ratio) are studied. The test results show that: UHPC and concrete beam using chisel processing technology, unbonded prestressed by end anchorage can achieve effective interface bonding while ensure the reinforcement effect with a simple construction process; Prestressed UHPC reinforced beams can greatly improve the cracking performance, flexural bearing capacity and rigidity; Through theoretical research, the formula of flexural bearing capacity of ordinary concrete beams reinforced by prestressed UHPC is deduced, which is conducive to subsequent engineering application.