Research On Temperature Effect Of Prestressed Concrete Box Girder With Corrugated Steel Webs

The prestressed concrete box girder with corrugated steel webs (hereinafter referred to as PCBG), which is a new type of bridge structure, has developed fast and has been widely applied in recent years due to its distinctive mechanical behavior. Until now, researchers has focused on the study of shear and flexural strength of the bridge, yet few has been done on the temperature effect although the temperature effect may be significant. Thus, the thesis studied the temperate effect on PCBG based on the research of Lijiahe bridge, a medium-span bridge project. The main work and conclusions are summarized as followings:1) This thesis makes a thorough review of existent researches on temperature effect of concrete and steel bridge, and introduces the specification on how to consider the temperature effects from Chinese and international bridge design code. And then the principles in analyzing temperature field and effect of box girder are elaborated in details.2) With the temperature field analysis based on the measured temperature data for a typical medium-span bridge, Lijiahe bridge, the temperature distribution in each directions of PCBG is derived. Longitudinally:The temperature profile turns out to be uniform under the act of sunlight along the bridge. Vertically:The top slab temperature decreased gradually through surface to bottom in an exponential function form. The upper and lower part of web decreased slightly due to the influence of concrete, while the temperature at the lower part increased gradually through bottom to surface in a quadratic curve form. Laterally:The temperature in left or right side of the top slab varies in quadratic curve form. And the transverse temperature difference in web and bottom plate is negligible.3) Combined with finite element analysis by MIDAS/Civil software, the formula obtained in this study was applied to calcutate practical temperature effect for Lijiahe Bridge and Taohuayu Yellow River Bridge, respectively. The result indicates that when the sunlight is acting on the box girder, noticeable longitudinal and transverse stress was found which will further cause large principle tension stress of the structure. Therefore, in the bridge design, the temperature effect must be valued to avoid the possibility of concrete split. Meanwhile, because of the secondary stress and lateral moment produced by the transversely asymmetric temperature distribution, the pier top bearing will have the largest tempreture-induced secondary stress. The lateral moment has also changed greatly. Therefore the layout of the pier top bearing should be taken account of. The concrete diaphragm can constrain temperature deformation effect on the neibouring box girder, so that avoid unnecessary concrete diaphragm will reduce temperature effect.