Design–Build Replacement of US-90 Bridge over Bay St. Louis, Mississippi

As part of the rebuilding efforts after Hurricane Katrina, the Mississippi Department of Transportation awarded a design–build contract for the replacement of the 2.1-mi-long US-90 bridge spanning Bay St. Louis. With a January 25, 2006, start date, the deadline for opening two lanes of traffic was May 16, 2007, followed by a February 15, 2008, deadline for opening the entire bridge. The bridge was constructed as two separate structures except for the navigation unit, where the deck and substructure are continuous between the eastbound and westbound structures. To allow for such an aggressive construction schedule, several concepts were used. Plans were delivered in stages to allow construction to proceed before the final submittal. The use of precast components including girders, piles, and capbeams was maximized. Pile bents to a height of 75 ft above fixity were used, with no battered piles. The pile and girder sections were varied to allow for utilization of more precast fabricators. Precast, prestressed piles, ranging in length from 50 to 164 ft, form the bridge foundations of the pile bents (24- and 36-in. piles) and waterline footings (30-in. piles). Typical superstructure elements consist of BT-78 girders (maximum span of 154 ft) and AASHTO Type IV girders (maximum span of 112 ft). A spliced haunch girder system with a 250-tt main span and 200-ft end spans was implemented at the navigational channel to satisfy the vertical and horizontal clearances.