Complete Stay Cable Replacement for the Luling Bridge, First of its Kind in North America

摘要

Despite many advantages, there have been concerns for the use of stay cables in bridges including consequencesof stress concentrations at anchorages, corrosion, and vibration susceptibility. Deterioration has already beendetected in stay cables for some of the new-generation cable-stayed bridges. While the second cable-stayedbridge in the State of Louisiana was under construction across the Mississippi River, its first cable-stayed bridge,the Luling Bridge, had to go through replacement of all its cables only after 27 years in service. Inspections hadfound a variety of critical damages to the protective sheathing, and exposure and corrosion of the main tensionelements of the stay cables. Based on the results of a life-cycle-cost analysis and long-term considerations, theLouisiana Department of Transportation and Development decided to replace all cables. This paper describes thereplacement design and construction activities completed in Fall of 2012. The cable replacement designaccommodated an extraordinary construction sequence to address constraints on space and traffic flow, thereforeprovided for no lane closures during peak traffic hours. Temporary cables minimized stress variation, and allowedfor the live load without restrictions. Special lifting devices and installation methods reduced the need forconstruction space. The new cables utilize parallel strand system consisting of individually greased and sheathedseven-wire strands, all encased in PE sheathing. This system allows individual strand installation and tensioning,and is expected to facilitate future inspections and replacement. The cable replacement design and itsimplementation contain unique aspects, and are the first attempted in North America.