Research On Long-Term Performance For High-Pier&Long-Span Continuous Rigid-Frame Bridges

High-pier and long-span continuous rigid-frame bridges play a dominant role of span40～300meters due to its merits gradually, which are good mechanical properties, easy to be constructed and long-span etc. However, with the increasing service age of bridges, cracks, excessive mid-span sag of box girders and the loss of effective prestress exist in built bridges during service, which had extremely negative influences on the long-term performance of bridges. In view of those, taking the Longtan River Bridge of Hurong Speedway in Hubei Province as the engineering background, the long-term performance is studied in this thesis. The main research work is summarized as follows.(1) Summerized the influencing factors of long-term performance for bridges on the basis of extensive research materials at home and abroad, and concludes that the concrete shrinkage and creep, prestressing loss, temperature load and overload, unequal settlement of pier, cyclic loading are the main factors.(2)Field-tests for stress variation of control section of Longtan River bridge were conducted in extreme weather conditions after its completion in two years. Compared with the current prediction models, the JTGD62model was finally used to conduct simulation analysis by using finite element analysis software of MIDAS/CIVIL, the calculation results and field measured results were compared. The results showed that the bridge was in safty during servise and confirmed the JTGD62model can be used well for studing the shrinkage and creep long-term effects of Longtan River bridge.(3) The shrinkage and creep effects of Longtan River bridge during servise were studied based on JTGD62model.The result shows that shrinkage and creep had extremely effect on high-pier and long-span continuous rigid-frame bridges,such as structural deformation,the stress of both the top and bottom sides of main beams and pre-stress losses of tendon.(4)The influence of the annual mean temperature difference load on structural deformation and the stress of both the top and bottom sides of main beams for Longtan River bridge were studied, the result shows that the influence of annual mean temperature difference load on performance of high-pier and long-span continuous rigid frame bridges cannot be ignored. In addition, the influence of shrinkage and creep on long-term deflection of main beams in different conditions of temperature was studied, the result shows that the higher temperature it was, the greater effect of shrinkage and creep on the long-term deflection of main beams of bridge structure.(5) The influence of prestressing loss on deflection and stress of both the top and bottom sides of main beams for longtan river bridge was studied quantitatively.It was shown that prestressing loss is the one of the main reasons that increased long-term deflection and cracks of main beams. In addition, the influence of the prestressed pipe friction parameters μ、k on deflection of main beams was studied.The results shown that the reasonable value of friction parameters μ、k can effectively control the deflection of main beams of high-pier and long-span continuous rigid frame bridges.