Reinforcement Mechanism Of External Prestressed Concrete Box Girder Consist Of SMA

Based on the problem of the early crack and long term deflection in large span PC box girder bridges, combined with the development and application of the new functional material.Based on the laboratory test and theoretical analysis, this thesis Study of the Intelligent Strengthening mechanism with SMA wires for the concrete box beam.The main works of this thesis are:These material mechanics behaviors of SMA wires, According to DSC, we can get that processing technologies have effects on the material properties of SMA wires, and get the transformation temperatures of the SMA wires. Researches of bonding tests of the SMA wires indicate that the bonding performance between SMA wires and epoxide is very bad, therefore, This paper studied a new-style SMA wires anchorage device, The results show that it is feasible to anchorage SMA wires.During tensile test of SMA wires under normal temperature, the phenomenon of necking cannot be observed, the results show that the super elastic mechanical properties of SMA wires. The researches of recovery force of SMA wires show that the force is increases as the temperature rises at fully constrained conditions, there have a direct proportion between the maximum values of recovery force and pre-strain.The force analysis and experiment capability research of unbonded SMA intelligent concrete box beam, that, when The initial prestressing of the SMA wires was5%, After electrifying of SMA wires,the mid-span deflection of the concrete box girder reduce7.6%,the strain of concrete reduce14.4%, the rebar strain reduce13.4%, the observed maximum crack width re-closes about34%.the load capacity and stress performance of the concrete box beam could be effectively improved by SMA wires, the intelligent concrete box beam have good self-rehabilitation capabilities.The results of non-linear FEM analysis of the concrete box beam with SMA wires show that, the experimental and the analytical results agree, the concrete box beam with SMA wires have a better self-rehabilitation capabilities, without the unfavorable factors.