Study On Prestressing Effect Of Prestressed Concrete Continuous Rigid Frame Bridge With Long Span

Prestressed concrete structure is one of the most important engineering inventions in20th century. As early as1861, people had proposed the idea of exerting prestress on concrete and they started various kinds of work on test and research. The use of prestressed concrete makes the forms of bridge structure becoming more diverse. Among them, with the advantages of driving smoothly on bridge deck, free of changing bearings of piers and system conversion, continuous rigid frame bridge shows many advantages in engineering projects. So it has achieved rapid development in the past four decades. The maximum span of it has exceeded300m. This thesis does some research on prestressing effects which are based on a project of prestressed concrete continuous rigid frame bridge with long span. The main contents are described below.1. The calculation methods of prestressing loss for bridge are summarized. The characteristics of prestressing effect and multiple kinds of prestressing loss are analyzed. The influence of materials and the influence of processes on prestressing effect are generalized.2. According to finite element method, the solid model for structure which includes prestressing tendon element is established. The law of prestressing effect is analyzed under the influence produced by dead weight of the structure, shrinkage and creep. It is used to compare with the result of a beam element model.3. The solid element model which considers shrinkage, creep and the change of elastic modulus is established. The influence of concrete age on prestressing effect is analyzed in the model which considers the influence of dead weight and prestress.4. Considering the shrinkage, creep, temperature and other factors, the influence on prestressing effect produced by lag time of tensioning vertical prestress tendon is analyzed from the perspective of strain.5. Normal longitudinal stress of top plate and bottom plate is analyzed in the situation with transverse prestress and the one without. It is proposed from the analysis that characteristics of the spatial distribution created by normal longitudinal stress of top plate and bottom plate. The influence on normal longitudinal stress which is created by transverse prestress is also proposed.