HUEY P. LONG BRIDGE WIDENING — SUBSTRUCTURE
New Orleans, Louisiana
The US 90 Huey P. Long Bridge is one of three vital Mississippi River crossings in the New Orleans area. The combination railroad and highway bridge, 2400 feet main span, was completed in 1935, and carries two lanes of traffic in each direction. The state of Louisiana, under the TIMED program, determined the optimum method to increase highway capacity was to replace the existing lanes and widen the bridge to three lanes each way. This unique substructure work included widening the five main span piers.
The widening was accomplished by installing concrete encasement of the original bridge piers up to Elev. 90 feet MSL, and structural steel frames to Elev. 145 feet. The original bridge piers, founded on dredged caissons, have sufficient capacity and size to carry the additional traffic lanes and loads. The new structural concrete started at Elev. (-)6 feet MSL, below normal river stages of Elev. 4 to 10 feet MSL, and was installed by the use of limpet cofferdams attached to the existing piers.
The project’s location and scope presented several challenges to the Massman team. Crane barge access in the main river channel required constant coordination with Mississippi River shipping and barge operators. The river depths approached 90 feet which required substantial anchoring of crane barges. Work was suspended for several extended periods due to river flood stages and tropical storms. The river currents and swift eddies near the piers required divers and marine equipment to operate safely.
The concrete encasement, for a total of 17,000 cubic yards, included drilling for 16,000 anchors to the existing piers and lateral post-tensioning. The structural steel frames required 20 critical crane barge lifts of 150 to 200 tons. The 4500 tons of structural steel fabrication required special procedures due to the precise fit-up of heavy sections and fracture critical welding requirements. The structural steel was fabricated, pre-assembled, and shipped by barge to the job site.
