MaineDOT officials say they have learned something new with every BIAB project. "With LaGrange, we struggled with some of the connection details on the way the arch fits together on the 56° skew," Frankhauser says. The agency has used CAD drawings as part of its planning but may employ 3D modeling for future projects to more accurately represent angles and save time.

The Michigan Dept. of Transportation completed a BIAB structure last August on the east coast of Lake Huron. It took nearly two months to put the BIAB arches on piles and complete both abutments, and the work required heavy equipment usually used to build a conventional bridge, says Matt Chynoweth, Michigan DOT bridge field-services engineer. While arch bridges perform well in the mountains, Michigan's clay and sandy soils require deep foundations, he says. "We also had issues with the self-consolidating concrete and had to add retarders, since the nearest con-crete suppler was 45 minutes away," Chynoweth says.

Extensive testing of four full-scale bridges is under way at the University of Maine with the goal of proving that loads on the foundations are less than those specified in typical designs, so agencies can cut down on the size of foundations, says Habib Dagher, founding director of the Advanced Structures & Composites Center at the University of Maine.

With support from a $1.4-million U.S. Dept. of Transportation grant, AIT and University of Maine researchers also are developing a splice system to build longer spans. The external tubular splicer system will enable splicing between two or three tubular arches, says Dagher. "This opens up more opportunities in different locations and for longer spans."