Research On Stress Monitoring Of Prestessed Concrete Girder Bridges

Large-span prestressed concrete girder bridges which possess many advantages including high stiffness, good integrity and mature construction have widely been used in the bridge types. In order to ensure the safety of the bridge construction and linear state after completion consistent with the design, the bridge construction processmust be monitored and controlled. It is important to stress monitoring in monitoring and control of the bridge construction process, it is not only related to quality and safety of the construction, but also verify the accuracy of the theoretical calculation method. Therefore, stress monitoring must be noticeable in monitoring and control of the bridge construction.The basic method of prestressed concrete girder bridges stress monitoring is the indirect method. its basic idea is that the concrete measured stress is calculated by concrete measured strain. In the process,it needs to accurately deducted non-stress strain caused by creep and shrinkage etcfrom the measured total strain of concrete. Traditional specification formula method directly uses the given creep and shrinkage specification of concrete and parameters to calculate the concrete creep strain and shrinkage strain, it dependents on the shrinkage and creep parameter values heavily, so it cannot guarantee the accuracy of the the concrete measured stress.According to the above problem, neutral axis calibration method is presented in this dissertation, it based on neutral axis stress of girder relative insensitively to the construction load of prestressed concrete girder bridges, shrinkage and creep parameters is identified through the girders neutral axis stress, using these shrinkage creep parameters to calculate girder and lower edge stress. This method can grasp the shrinkage and creep parametersat some degree, improve the accuracy of the concrete stress calculation. But this method can not be guaranteed to meet the characteristics of the flat cross-section deformation of prestressed concrete girder bridges, concrete calculation accuracy is yet to be improvedfurther. For this reason, this dissertation further puts forward the proportional reduction method, this methodis through the neutral axis stress calibration of prestressed concrete girder bridges, reduction proportion is calculated by deduction of creep and shrinkage strain of the neutral axis, using characteristics of flat cross-section deformation, reduction proportionis used to calculate the superior and inferior marginsstress, the calculation precision of the concrete stress is improved further.