The Application Of Pre-stress Concrete U-Shaped Beam In Road-Bridges

Bridge was an important part in the construction of highway and city road, especially, the great and fit- size bridges had an important meaning to a country's politics, economy and national defense. Recent years, the construction project of domestic highroad, especially the highway had been developed quickly. As an important part of the highroad, the construction of the bridges had also been developed, emerging many types of bridges structure. The Pre-stress Concrete U-Shaped Beam was a newly type bridge structure, it had many merits compared with the traditional pre-stress concrete bridge structure like box-shape and T-shape beam, including low height, short length of the bridge approach, saving soil resource, lower project investment and shorten engineering structure period and so on, it also fitted to be applied to plain region and the places which limited the utilized soil resource and the bridge required net-height.Many research indicated that the Pre-stress Concrete U-Shaped Beam structure had many disadvantage compared with other type bridges, such as poor torsion resisting ability, the big lag effect of shearing force etc, affecting the application of the Pre-stress Concrete U-Shaped Beam structure in bridges. In our country, the research about the torsion and the shear-lag of the U-Shaped Beam structure was insufficient so that the Pre-stress Concrete U-Shaped Beam hadn't been popularized in domestic roadrbridges.In this paper, firstly a set of analysis theory method based on the energy Variational Method brought forward by E. Reissners about the shear-lag effect of box-beam was applied to the shear-lag effect problems to calculate and analyse the shear-lag effect of the full beam under different load. The influence of the geometry of the U-shape section and the material parameter on the shear-lag effect was also taken into account. At the same time, a set of torsion analysis theory was set up to calculate and analyse the torsion resisting ability and its whole stabilities.The project of DengZhou bridge using Pre-stress Concrete U-Shaped Beam structure was considered in this paper, using finite element analysis software ANSYS6.0 to make numerical analysis under different combined loads such as the self-weight of the beam, pre-stress and the weight of the trucks. Well agreement was obtained between the result of numerical analysis and the result of theory research, these results proved that the theory method built in this paper to analyse the shear-lag effect and the torsion of the Pre-stress Concrete U-Shaped Beam structure was feasible, which builts a stability theory for the popularization of the Pre-stress Concrete U-Shaped Beam structure for the future.