Static Performance of a Long-Span Concrete Cable-Stayed Bridge Subjected to Multiple-Cable Loss during Construction

Abstract

To study the structural response of a long-span cable-stayed bridge to cable loss during construction, the static performance of the Chishi Bridge subjected to multiple-cable loss caused by a fire accident was investigated in detail by field inspection and finite-element simulation. Nine cables on the same cable plane ruptured successively during the fire accident. As a result, the cantilever end of the girder dropped by 2.08 m, and the girder cracked severely. The cable tension, the displacements, and the damage state in the girder and pylon were measured to verify the nonlinear finite-element model. A comprehensive numerical study was then conducted to analyze the structural behavior of the bridge throughout the process of cable loss and subsequent restoration. The results from the field inspection and simulation showed that (1) the obvious change in cable tension and concrete cracking occurred in only the remaining cables and part of the girder within and around the cable loss area; (2) the loss of nine cables in the local area caused the combined action of torsion and biaxial bending in the girder, and resulted in dense distribution of diagonal cracks in the top slab and box girder webs; (3) after the accident, the maximum tensile stresses in the remaining cables and prestressed tendons reached 1,495 and 1,546 MPa, or 89.3% and 92.3% of the yield strength of steel strands, respectively, while the maximum principal compressive stress in the box girder reached 29.8 MPa, or 83.9% of the concrete compressive strength; and (4) the global structural performance of the damaged bridge recovered very well when the temporary cables that were added to replace the broken cables were jacked to the original design tension, indicating that the global behavior of the cable-stayed bridge was mostly controlled by the cables.