Prestress Loss And Sensitivity Analysis On The Linear Of Long-span Prestressed Concrete Continuous Bridge

Long-span prestressed concrete bridges and cantilever construction method have been widely used in the whole country. Cantilever construction method is relatively complex. The main girder alignment must be changed and the difficulty of construction monitoring can be increased during the construction period. The main works in the construction monitoring are to monitor and deal with parameters. In order to improve the monitoring accuracy, the software of Midas/Civil is used for analyzing the sensitivity of parameters during the construction period, based on a long-span prestressed concrete bridge in Foshan City, Guangdong Province. The main contributions of this thesis are included below:(1)Based on the construction steps of Huayang grand bridge and the principle of finite element, the model of this bridge is built and simulated by using the Midas/Civil. Then, the values of theoretical elevation and prestress loss in every construction step can be calculated.(2)The parameters, concrete density, elastic modulus of concrete, initial tensile stress, construction load, parameter of tube friction resistance loss, shrinkage creep of concrete, that influence linear of the main beam during construction period are analyzed sensitively. The main parameters of affecting alignment and the influence degree of each parameter are found out.(3)According to construction step, the plan is formulated that elevation monitoring. Data is obtained and compared with measured data by simulated, which is to prove the model reliable. Some prestressed strands are monitored by magnetic flux sensor to gain their effective stress, which is analyzed and compared with the calculated results by model.(4)With the practice of the project, the situations are analyzed to get the influence for the following construction, such as improper operation of construction process, change of unit weight of concrete beam, increase of prestress loss of the steel beam, change of the parameter of tube frictional resistance. The reasonable solutions are benefit for the following construction and provide accurate reference data for construction monitoring.(5)Magnetic flux technique is used for monitoring some prestressed steel beams for the purpose of obtaining their effective stress and law of prestress loss. The law can be predicted effective stress of prestressed steel strands unmonitored, which is calculated the proportion of elevation caused by the effective stress among the measured elevation of the bridge. It provides scientific basis for the measure to reinforce the bridge.