Study On Deflection Control Of Large-span Prestressed Concrete Girder Bridges

This paper mainly surrounded the excessive midspan lag which was a main problem of large-span prestressed concrete girder bridges at present,make a brief summary of the survey of development, characteristics and common diseases of large-span prestressed concrete girder bridges at first;this was followed by the comparisons of structure characteristics, internal forces and vertical displacement of different long-span prestressed concrete girder bridges and the analyses of inherent laws among those factors,which aimed at three different long-span continuous beam and continuous rigid frame bridges ;then prestress,selfweight of structure, box girder rigidity, concrete creep and shrinkage,first time loading age of box girder segments and combined effect of multiple factors were studied to compare their influences on deflection,and then summarized various possible causes of excessive vertical displacement especially long-term excessive vertical displacement of large-span prestressed concrete girder bridges;finally focused on the study of deflection control programs which using top slab tendons, bottom slab tendons, reducing selfweight of the upper structure or using cables, as well as combining programs based on the above-mentioned deflection control programs, with a hope to offer reasonable proposals for the design and construction of those bridges.