Analysis On Creep Effect Of Prestressed Concrete Continuous Box Girder Bridge

Concrete creep is the phenomenon that the deformation of the concrete structure will continuously increase with the time going under the action of continuous load. On the current research point of view, there are many factors that affect the change rule of creep, such as the nature and composition of materials, the environment temperature and humidity when components are poured and maintenanced, the ratio of surface area and volume, the environment temperature and humidity, loading history and the nature of the load, etc. So far it is difficult to get mathematical model of creep that can reflect the actual characteristic of the material accurately. Because of the complexity of the construction process and variability of the environment, it is hard to accurately analyze the impact caused by concrete creep of prestressed concrete continuous box girder bridge with cantilever casting method. The analysis of creep effect of prestressed concrete continuous box girder bridge with cantilever construction has a great significance for the construction of continuous beam bridge and the good performance of the bridge after completion.Lao Wan Fu River Bridge is a bridge project that pass through the Wanfu River of Ji'nan to Xuzhou highway jining yutai region. The superstructure of the bridge with three span(55m+90m+55m) variable cross-section prestressed concrete continuous box girder. This paper takes the Lao Wan Fu River Bridge as the engineering example, on the basis of the relevant literature, the mechanism of concrete creep, influence factors of creep, theories and methods of calculation are discussed briefly. The finite element model of Lao Wan Fu River Bridge is established using the bridge engineering professional software Midas/civil, further research is carried out about the creep effect of continuous box girder bridge combining the common problems of engineering by the numerical simulation.In this paper, the research contents mainly have a few aspects as follows:(1) On the basis of referring to the relevant literature, the related theory of concrete creep effect and its calculation methods are summarized.(2) The Midas model of Lao Wan Fu River Bridge is established, and the creep effect of different operation period and different long term load(self-weight of the structure and secondary dead loads?prestressing force) is analyzed and calculated.(3) Established models of the cantilever construction period is 5 days, 7 days, 10 days, 15 days and 20 days through Changing the construction period of cantilever segment, and analyzing the iMPact of different periods of cantilever construction on the creep of bridge girder concrete in different operation period.(4) Changing the construction time of the bridge deck pavement to establish the different working conditions model, by 10 days, 20 days, 30 days,......, and 120 days as the construction time of the bridge deck pavement, and analysing the creep effect of the bridge under different operation periods.(5) Analysing the influence of different closure sequence on creep of bridge in operation period according to the first side span across and across the first side span closure sequence in the model.(6) After the analysis of the engineering example in this paper, the creep effection of the corresponding span prestressed concrete continuous gider bridge is concluded, and references for the construction of similar bridges are given in the future.