Study On The Design Method And Construction Technology Of Prestressed Concrete Simple Supported-continuous Box Girder Bridge

With the continuous economic development of our country, the construction of the highway has got great-leap-forward development. The traffic mileage of the highway has reached 53 ,000 kilometres in 2008, which is the second all over the world. The"Five Longitudes and Seven Lantitudes"national trunk highway has already transfixed. The small and medium span bridge is about 310,000, which is over 90 percent of the open-to-traffic road bridges. The percent for the road bridge that the small and medium span prestressed concrete simple supported-continuous girder bridge accouts has increased year by year. Compared with other kinds of bridges, prestressed concrete simple supported-continuous girder bridge has so many advantages that it is used more and more. In abroad, this kind of bridges have been used very widely in bridge project construction, while at home, the design and construction level has been greatly improved. Novedays, the use of prestressed concrete simple supported-continuous girder bridge in bridge project has already been popularized and extended greatly.This paper briefly introduced the finite element theory which is the basic theory of the bridge computation. It provided the solutions of the nonlinear equations as well as the material nonlinearity finite element theory and the geometric nonlinear finite element theory. The finite element theory is the foundation of the bridge computational mechanics, which is also used for the understanding of the bridge computation and analysis through the introduction of the finite element theory.Taking Shitouhe bridge that is a finished highway bridge project for example, using the computing software Doctor Bridge, this paper completes the analysis and computation of the forced state and the construction technology control of the small and medium span prestressed concrete simple supported-continuous girder bridge. The analysis and computation of the superstructure is satisfied to the current codes and the structure is basically reasonal.At the finished stage , the beam bottom compressive stress of section near the support is too large, which is related to the geometric features that the box girder is wide in the up part and narrow in the down. It is suggested that the beam bottom which the bearing negative moment effects be thickened in the following similar bridge design. Because of the design continuous length of the near span is long (150m), the internal force at the pier tops of the continuous beam are not homogeneous. Our province is in the seasonal frost region. Construction temperature (15℃) and the extremely low temperature(-30～-40℃)are very different, which results the horizontal force of the boundary pier accumulates too large. It must to make sure the stiffness of the substructure is large enough. It is suggest that the single continuous length when designing the similar bridge should be less than 150m, which can obtain a good economic effect.Taking Shitouhe Bridge for example, comparing the compute results of the vacuum grouting technique with plastic corrugated pipe and the zinc-iron corrugated pipe under usual design, as well as the increase of thetension control stress and the former design, it reaches the conculusion that the improvement of the construction technology is very important to improve the performance of the prestressed stell. Visiblely, in the following projects, improving the constucution technology and increasing the mechanical performance will play a very important effect in popularizing and developing the Prestressed Concrete Simple Supported-continuous Girder Bridge.