Analysis Study On Creep And Shrinkage Effect Of Prestressed Concrete Bridge With Combined Model Of Solid Element And Bar Element

The creep and shrinkage of concrete is a phenomenon that deformation of structure increases with time under sustained load. According to practice of engineering, creep and shrinkage of concrete will account for a large proportion of concrete deformation. Creep deformation usually accumulates to 1.5~3 times of elastic deformation under the same stress state and has great influence on the long-term deformation of concrete structures. In the prestressed concrete structure, creep and shrinkage are related to reinforcement ratio. Creep and shrinkage occur in concrete, meanwhile steel hasn’t these properties and will restrain creep and shrinkage of concrete. Thus it leads to stress redistribution and prestress loss. For bridges of changing structure system in construction and indeterminate system, creep and shrinkage will cause internal force redistribution. So deformation caused by creep and shrinkage is a key factor which must be taken into consideration in the design of bridge.Nowadays, mainstream of calculation in concrete creep and shrinkage is established on the base of beam element. Reinforcing steel bar is taken in account by the means of transformed section method. In this method, steel will also have the behavior of creep and shrinkage, which is not reasonable in physical concept. In this article, a new method is put forward. The fine finite element calculation model combined with three-dimensional solid element and bar element used to analysis creep and shrinkage of prestressed concrete bridge structure, in which solid element is used for imitating concrete, positive-area bar element for steel bar and negative-area bar element for channel. The displacement constraint equation combines solid element and bar element. The prestressed forces of steel bar are applied by the means of adding internal force of bar element. On the basis of this finite element model, changing structure system in construction and creep and shrinkage are taken into account through the method of step accumulation. And finally a module is established. This article gives the key techniques and ideas used in this module and the validity of this module is also verified by some example.