This project’s creation of modular, precast concrete open-cell boxes for use as pier fenders, replacing steel and timber versions, offers potential for many bridges around the country. The fenders on the I-10 bridge over the Mississippi River in Baton Rouge, La., typically are about 14 ft (4.3 m) wide, 11 ft (3.4 m) deep and 13 ft (4.0 m) tall. They begin 19 ft (5.8 m) below the water’s surface and extend 45 ft (14 m) above water, completely surrounding the pier.
Precast concrete modular boxes provided the structural core and formwork for the closure pours between box sections and the pier shaft. This eliminated the need to erect formwork in the field. All modules were cast prior to site work beginning to speed construction, which was further enhanced by attaching composite marine timbers and applying coal-tar epoxy prior to shipping.
The modular boxes allowed erection to be completed with vertical alignment guides. The boxes are gravity supported on the distribution block and braced for impact by concrete fill between the back of the precast concrete and face of the pier shaft. The open cell at each joint between boxes was filled with concrete to distribute shear and anchor a tieback. The mass of the system and remaining open cells allow for controlled crushing of the boxes to absorb and deflect impact.
Of the 138 modules used on the project, 100 were side modules, 20 were corner modules, 10 were nose modules, and 8 were created as replacement sections for future repairs from major impacts.