Research Into Building Model Based On Grid Structure Theory Of Curved Box Girder Bridges

With the rapid development of expressway and main road, more and more interchanges and fly-over crossing will be built. The curved box girder bridges have been adopted more and more in the bridge project of interchanges and fly-over crossing because of good performance of structure and features of economy, beauty and utility. However, because of complex features at some aspects: mechanical character, load, constitution and construction, some problems will be solved urgently, especially the theory of analysis and calculation. Now there are several theories, but these theories aren't good at engineering design in fact, and the grid theory is a good choice. However, modeling appropriately affects on results of calculation. How to build properly model will be researched further.Modeling properly of the curved box girder bridge is discussed in three aspects, and several favorable results to model building are achieved in the paper.First of all, mechanical characters of the curved box girder are analyzed in the paper. With reference to the experience of scholars and the author's experience of engineering design, several suggestions are put forward in the dividing mesh and defining parameter of cross-section, and an example is used to explain.Second, on the basis of classical girder theory, girder element stiffness matrix considering shearing deformation is deduced, the method of calculation of value of shearing deformation is illustrated, and how far effect on inner force and deformation considering sheering deformation is discussed. Through comparison inner force and deformation between considerations in shearing deformation and not, several results are achieved and several suggestions to calculation are pointed out.Third, prestressed reinforcement is considered in the paper. According to relationship of master-slave restraint, the displacement relationship between cable element and beam element named as coordinating relations of steel andconcrete in the space is deduced. According to the coordinating relations, initial strain is used to implement prestressing in the program. Then, when inner force and deformation are calculated in the analysis of construction stage and performance stage of bridges, creep and shrinkage of concrete can be considered automatically, and when batching cable wire is stretched or the way of stretching need be simulated, loss of prestressing force can be calculated automatically. Then computational efficiency and precision are increased.In the end, a curved box girder bridge of interchange in XiaMen and South Lake Bridge in WuHan are analyzed by the WXQ program developed by Professor He Xiongjun, and the results of inner force are compared with results that calculated through another method. So rationality of model building is demonstrated.