The is now open to traffic over the Pierre Part Bayou in Assumption Parish.
Originated with an Investigational Bridge Research Deployment grant in association with the Louisiana Transportation Research Center, the development of the composite bridge deck was jointly undertaken by the Louisiana Department of Transportation and Development Louisiana State University, Crescent City Composites, and the Technical Services team of Alcan Baltek.
Using balsa-cored composite panels has many advantages as the lightweight composite panels allow for fabrication off site and are quick to install. This results in a reduced closure time for the bridge and less traffic disruption, on a road which is an important evacuation route during Hurricane season. In addition, these panels are immune to corrosion which shortens the life span of steel structures, especially over brackish waters.
Being replacement panels for existing steel construction means that the geometry, specifically the thickness of the panel, is dictated by the existing bridge structure. In order to achieve the required stiffness within the restricted thickness, layers of Hardwire® high-tensile strength steel reinforcements were used in conjunction with conventional biaxial glass fibre in the structural skins.The core chosen for this application was a specific density range of BALTEK end-grain balsa. This material can absorb both the high compression loads required of a bridge, and the high shear loads imposed by the restricted thickness and highly-loaded metal and glass fibre skins.
All panels were vacuum-infused on site at the Crescent City lamination facilities in East Texas and transported by road to the Louisiana Department of Transport in Baton Rouge, where they were adhesively bonded to steel girders. Future production is expected to take place in Louisiana.
“This joint development project promotes composite construction as an alternative to steel or concrete bridge structures,” says Alcan’s Marc Anderson. “The composite bridge deck design is expected to be the first of many in Louisiana to replace traditional steel grating structures over these many regional bayous.”
As part of further research, Louisiana State University has installed fibre optic strain gauges in the bridge panels to monitor the performance of the laminate over several years. The Technical Services Department of Alcan installed conventional strain gages on an adjacent deck plate, to compare load responses for both methods of monitoring. This monitoring is of particular importance because half of the composite panels on this bridge incorporate SWCNTs in the vinyl ester resin of the laminate, resulting in significant increases in flexural strength and fatigue properties.
