Abstract
The problem of cracking and long-term deflection in larger-span prestressed concrete box girder bridges exists throughout the world and has restricted the development of long-span concrete bridges to some extent. However, the understanding of cracking and deflection of concrete box girder bridges is still insufficient and many strengthening methods cannot reach anticipated effect. In this paper, a space-frame lattice model which is used to analyze the stress on the entire cross-section of the box girder bridge, is presented. The stress state of random grid elements in the model may be biaxial in plane. The model simulates the cracking and deflection of pre-stressed concrete box girder bridges. This model was applied for cracking and deflection analysis of the existing concrete box girder bridge with (80+100+80) m spans. The calculation results are compared with the actual status of the bridge. The paper indicates that cracking of girder becomes one of major factors which have influence on deflections of long span prestressed concrete bridges. The space-frame lattice model is an effective tool to analyze the cracking and deflection of prestressed concrete box girder bridges and merits further investigation.
Highlights
The box girder with a closed cross-section, which has better global behaviour, larger torsion stiffness and an effective top and bottom concrete flange in compression, is widely used in large bridge structures
The prestressed concrete box girder bridges, which are suitable for various modern construction methods, have superior applicability
Since the 1970’s, prestressed concrete box girder bridges have been predominately applied in the design of bridges with medium- and long-spans
Summary
To try to find the influence of cracking on the deflection of a structure an actual bridge with cracking and deflection was simulated and analyzed by the space-frame lattice model. This bridge is a prestressed concrete continuous box girder bridge with (80+100+80) m spans, completed in 1995. The bridge contains the whole internal prestressing system, i.e., tri-directional prestressing system in longitudinal, transverse and vertical directions (Fig. 8). The inclined cracks in the box girder webs were numerous within 5 m of both side-span 1 supports. Many parallel cracks in the longitudinal direction of the bridge existed along the bottom slab of the box girder at mid-span of both side-spans.
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