Michigan contractor J. Slagter and Son Construction Co. was recently chosen by the Michigan DOT to perform structural repairs on the M-40 Bridge through Hamilton, MI and they trusted Mabey Inc. to provide the bridge jacking and structural shoring solutions to help them do it. The bridge supports a significant volume of highway traffic but the bridge bearings had become worn, the deck cracked and concrete repair was needed near the bridge’s girders due to years of wear and tear. Further complicating matters was the fact that the bridge crosses the Rabbit River and implementing any solution would require a product that could both support the bridge and remain flexible enough to work in relatively tight spaces. Product specialist Jim Porreca teamed with engineer Andy Wilkin to develop a solution utilizing Mabey’s Mat 75 structural shoring system to get the job done.
Initially, the Michigan DOT developed a plan that included driving interlocking sheets into the ground immediately below the bridge. The contractor would then de-water the site and place any bridge propping equipment they needed there. Unfortunately, a low clearance and concerns for nearby traffic made those plans difficult to implement. Instead of driving sheets, J. Slagter created a base of steel beams at ground level extending beyond the bridge piers and over the water. The beams were anchored on the shoreline side by poured concrete and, when the Mat 75 tower was placed on the opposite end, it created a cantilevered base that provided a stable surface for the equipment and eliminated the need for sheet piling. Unfortunately, getting the Mat 75 equipment under the bridge was complicated due to bridge’s clearance height. General Foreman Ric Kreutzer determined that, by hammering small holes in the bridge deck, the gear could be lowered through the bridge by a small crane truck to the worksite. Rick also designed special roller bearings that were mounted to the tops of the columns, allowing the Mat 75 components to be hoisted off the side of the bridge, guided down then rolled into their final position by hand. Ultimately, the 16-leg tower was assembled in place, providing support to the roughly 20’ high bridge while work commenced.
Because of the strength of the Mabey system, and thanks to some ingenuity on the part of Ric Kreutzer and his team, traffic is permitted to flow during construction hours. Additionally, sparing the sheets saved J. Slagter the time (and money) that would otherwise have gone into installation and dewatering efforts. Construction on the first phase of the M-40 bridge project is expected to conclude on August 28. The equipment will then be moved the other set of bridge piers and the process will be repeated for the other half of the bridge.