THE REHABILITATION OF THE THIRD SHIQIAO BRIDGE BY EXTERNAL PRESTRESSING

The cracks on the web of box girder for the third Shiqiao Bridge are demonstrated by pictures including the location and geometry of the cracks.The deficiencies of performance and cracks due to the incorrect design of web and the lower shear resistance are discussed.In order to suppress the crack propagation and improve the shear strength of the web,the external prestressing method is proposed after several debates.The formation of external prestressing cable,the arrangements and control stress of tendons are discussed.Some critical aspects,such as deviator and anchorage,are designed carefully.The analytical model is developed by bridge software,the internal forces and stress have been calculated by computer.By comparison,it can be known that the safety margin increases and the crack propagation can be suppressed efficiently.