Widening the Huey P. Long Bridge

摘要

The Huey P. Long Bridge is a high-level, combined highway and railroad bridge crossing the Mississippi River just upstream from New Orleans. The structure was completed in 1935, and at 22,996 feet from abutment to abutment is one of the longest high-level railroad bridges in the world. The bridge carries two railroad tracks within the through-truss main bridge and a narrow, 18 ft. wide, 2-lane roadway bracketed off each side of the through-truss structure.The roadway capacity is now, nearly 70 years later, inadequate for the region's needs. After initially considering a new river crossing, the Louisiana Department of Transportation and Development decided to widen the existing bridge roadways. The two roadways are proposed to be widened to 43 ft. each, to provide 3 lanes with a refuge shoulder in each direction. Two new trusses will be added to form a "three barrel" structure. This paper presents some of the difficulties in designing the proposed project including: 1) the need to maintain rail, vehicular and marine traffic throughout the construction period; 2) an assessment of the ability of the existing caisson piers to carry the increased loads; 3) a determination of the remaining safe fatigue service life of the existing steel truss superstructure; and 4) the incompatibility of erection deformations of the new trusses with the position of the existing trusses. Adopted solutions to these difficulties are presented.