The Ohio Dept. of Transportation completed the state’s first slide-in bridge project on Oct. 17-18, although on a somewhat different schedule following the discovery this summer of excess camber in two precast-concrete beams.

Part of a three-year, $71-million multiyear program to widen about 31 miles of Interstate-75 between Perrysburg and Findlay, the $7.8-million slide-in replacement of twin steel-beam structures, spanning U.S. Route 6 in Bowling Green, originally was set to begin in early August on the northbound lanes. But ODOT discovered that two of the reinforced-concrete W24 x 94 I-beams that supported the two-span, 198-ft-long, 60-ft-wide replacement structure had not deflected to specifications following addition of the deck. This resulted in excess curvature at two locations in the slab.

ODOT elected to move forward with replacing the southbound bridge of I-75, following a redesign of its beams. Originally set for the Oct. 10-11 weekend, work was delayed a week when bearings used for the slide-in process were refabricated for undisclosed reasons. ODOT would not say who will be responsible for the additional work.

Kokosing Construction Co., the Westerville, Ohio, contractor for the slide-in bridges, and project engineer ARCADIS referred inquiries about the project to ODOT. The agency declined to identify the fabricator. It also has not determined whether the excess camber was caused by a design or material flaw, what modifications may be needed to correct the problem or who will bear the cost of repairs.

Once underway, the southbound slide-in proceeded largely as intended, with most of the first day devoted to demolishing the existing four-span bridge, which was a 297-ft-long, 44.3-ft-wide rolled-steel-beam-andconcrete deck structure. It was built in 1969 and reconstructed in 1999. The 4.5-million-lb replacement structure was pulled into place laterally by four jacks at about 8 mph and aligned with new approaches and stub abutments on H-piles set behind mechanically stabilized earthwalls on both ends.

Traffic on both I-75 and Route 6 was restored on Oct. 19. A new center capand- column pier on H-piles replaces the existing cap-and-column piers on spread footings. ODOT hopes to reschedule replacement of the northbound bridge later this fall. Begun in 2014, the entire I-75 widening project is scheduled to be completed in 2017.