Urban Rail Transit Elevated Bridge Creep Effect Analysis

The mechanics of creep and shrinkage is very complicated and many influential factors should be considered. So it is an important and complicated problem to predict the effect of the creep and shrinkage on the prestressed concrete bridge accurately. The ballastless track structure put forward a higher demand with the creep deformation of Elevated structure. So the control of long-term deformation of urban rail transit concrete bridge becomes a main problem in the process of design.According to the mechanism, the influence factors and the mathematical models of shrinkage and creep and the calculation methods of the creep effectiveness, simply supported beam and large-span continuous rigid frame bridge on the 4th line of Guangzhou railway transport was used as project sample in the paper ,the shrinkage and creep effects for are analyzed. The major work of this paper is as follow:1,In this paper, on the basis of research results, the systematical generalization of the mechanics of the concrete shrinkage and creep and the internal and external factors affecting the concrete shrinkage and creep are made. The mechanisms, applicability and merits and faults of several prediction models at home and abroad on the shrinkage and creep are compared and analyzed, establishing the basement of proper selection of prediction models in the analysis of shrinkage and creep effect of practical structure.2,Several methods for the shrinkage and creep effect of concrete are researched comparatively in the paper. The age-adjusted effective modulus method is researched. Taking into account the concrete shrinkage and creep, the paper carries on the formula derivation of the finite element basic equation. Based on "the age-adjusted effective modulus method with finite-element step-by-step analysis method", the formulas to calculate the axial force and moment increment is presented.3,The thesis takes typical simply supported beam bridges on the Fourth line of Guangzhou railway transport as examples to carry on the structure analysis of shrinkage and creep effects after bridge finished. The results of the analysis are compared with the results though the long-term monitoring to test the correctness of the creep calculation model based on China's railways, highways bridges criterion. At the same time, sensitivity of the shrinkage and creep effects is analyzed.4,With shawan Bridge for engineering background, this paper carries on comparative analysis of the deformation, section-stress and prestress loss using different norms in order to analyze the law of creep deformation and internal forces. The comparisons of different heights of the piers, the construction methods of cantilever casting and cantilever erection on the creep are made. Combining deformation test results with the theoretical results, the paper verifies theoretical calculation is reasonable.