Research On Mechanical Behavior And Calculation Method For Box Girder Bridge With Corrugated Steel Webs

Prestressed concrete continuous box girder bridge with partial corrugated steel webs is a relatively new structural style, and the mechanical behavior for this kind of bridge has not been well acknowledged. Taking the bridge across Yong Xin River of NingBo as example, 3-D finite element method (FEM) was employed to investigate the mechanical behaviors of the bridge. The results were compared between 3-D FEM and expanded beam theory considering the effect of corrugated steel webs, and the precision of the expanded beam theory was discussed. The mechanical behavior and the load transferring mechanism in the connecting region between two different kinds of webs were also analyzed with 3-D FEM. Results showed that the precision for deflection and shear stress calculation with expanded beam theory based on the conventional box-girder theory is await to improve. The assumption that webs bear all the vertical shear force in the section is too conservative and uneconomical for design. The load transferring mechanism in the connecting region between corrugated steel webs and concrete webs is very complicated, the results from the beam theory can not reflect the load transferring mechanism, it is necessary to use the finite element method studying the connecting region with more consideration in design.For improving the analysis precision of the box girder with corrugated steel web, a new structural spatial analysis method has been proposed. According to the shell finite element theory, the proposed method was based on the simulation of corrugated steel web by orthotropic plate element and that of flange plate by isotropic plate element respectively. The two and three order displacement functions were introduced in axial and lateral direction in accordance with the deformation characteristic of box girder. The stiffness matrices and the vibration equation of structure were established by the sub-parametric element method to reduce the number of element and the amount of computation. From the comparison of the numerical example with the finite element program, the results showed that they are in good agreement under static and live load. As Compared with the current design theory of box girder with corrugated steel web the accuracy is remarkably improved, and the added amount of computation is within limit. This proves that the proposed method is useful in design of the box girder with corrugated steel web.At the same time, the mechanical behavior for the girder with corrugated steel webs during constructing were studied, the precision for the box girder with corrugated steel webs with expanded beam theory was more validated.