Huey P. Long Bridge Widening and Truss Lift Monitoring

The Huey P. Long Bridge is a four-span steel truss bridge that carries a two-track railroad line over the Mississippi River in New Orleans with two lanes of US 90 on each side of the central tracks owned by the New Orleans Public Belt Railroad. A bridge widening project was initiated to include two new vertical planes of trusses on the outside of the bridge and add additional lanes and shoulder over the complete four-span river crossing. As part of the overall bridge widening project, specifications were included in the construction documents to provide a truss monitoring system to compare actual versus predicted response of the bridge structure throughout the construction process of the original stick-build bid design. This monitoring system was intended to mitigate risk to the owner throughout the construction operation. When the contractor was awarded the project, a different method of construction was proposed where pairs of 528-ft long, 2700-ton trusses were built near shore on barges, barged in place under the bridge, lifted in pairs and skidded in place. A real-time remote monitoring system was designed and implemented to measure truss distortion and assure overstressing or buckling of the truss did not occur during the transport, lift and skidding operation. Data were under constant review to limit ‘sweeping’ of the truss during the lifting and skidding operation. This monitoring system was used to mitigate risk to the Contractor for the three pairs of heavy truss lifts.