Making it happen
24 April 2008
When veteran bridge builder PDM Bridge, LLC was faced with the challenge of transporting a large number of odd-shaped and very heavy bascule girders from its Eau Claire, WI fabrication facility to a Maumee River Bascule Bridge project site in Toledo, OH, they turned to Perkins Specialized Transportation Contracting, Inc. (PSTC) of Northfield, MN to make it happen. Too big to go by rail, PDM Bridge asked Neil Perkins and his team to come up with a highway solution to handle the eight massive fabrications totaling 740 tons of cargo.
After award of the project in June 2005 with deliveries set for November 2005, Perkins set forth a plan to handle the heaviest of the girders that were said to weigh 146,000 pounds each. As can happen on major fabrication projects, the schedule was forced to slide into early 2006, causing conflicts with PSTC's other contractual obligations. Once a mutually beneficial schedule was worked out, another new obstacle was presented - the larger pieces grew in weight to 182,000 pounds each. All of the preparatory work by Perkins'engineers and advance permit applications had to be revised to accommodate these larger pieces, no small chore when four states, each with their own unique demands for super-loads, were included in the designate dhaul routing.
Now less than 30 days to the first scheduled move in April 2006, the design team at Perkins dove into the problem. After they went through more than a dozen different CAD scenarios, each with their own “show-stoppers,” the Perkins team arrived at an elegant solution that impressed the PDM project team and was approved by the states.
PSTC decided to use, for efficiency, two complete hauling configurations each consisting of a single heavy-duty highway tractor with counter weighted drive axles for the maximum tractive force permitable on public roads.
These late-model powerful tractors, specifically designed and out fitted for super heavy loads, towed a configuration that included two 32-wheeled dual-lane dollies for the moves with an impressive GVW of 348,000 pounds with an overall length of nearly 170 feet and an overhang of nearly 29 feet.
Once the new method was finalized and approved, the Perkins operations team had only three weeks left to perform the necessary alterations to the two modular dual-lane transporters that were to convoy on every move.
As they were too tall to be transported upright, each of the huge bascule girders had to be laid on their side for highway hauling and supported longitudinally to avoid deformation. A strong-back beam was installed between the leading steerable dolly and its matching trailing dolly to provide support to the longitudinal axis of each piece.
Due to their odd-shape, locating the exact center of gravity was critical prior to loading. To do this, each beam was physically balanced at PDM Bridge's Wisconsin plant on woodenblocking to confirm the engineered center of gravity prior to loading onto PSTC's special hauling configuration to ensure equal tire loading. When the center of gravity of each girder was placed over the corresponding one for the transporter, it produced a symmetrical loads with long cantilevers at the end of the rig. The unusual cargo loading required carefully engineered tie-downs that included 130 perload ½ inch chains with ratchet binders to ensure the best possible securement. This additional weight had to be calculated into the overall gross vehicle weight of each load to ensure permit compliance with allowable axle loadings.
After a six-hour loading time at the Eau Claire facility the Perkins crew used its own scale equipment to verify axle loads on each of the two haulers before departure. Leaving at midnight on each of the loads, travel time was one day for each state, a total of four days per pair of loads, to allow the “changing of the guard” - a new set of police (as many as six in one state alone) and civilian escorts as required for each state. Significant coordination was required by the Perkins project management team to make sure that no delays were incurred due to permitting or escort requirements, a strong suit for this heavy hauler. Though interstate highways comprised most of the route, highway construction in Wisconsin forced the loads onto secondary highways through small towns requiring a lot of tight, very careful turns.
When they reviewed Perkins' CAD drawings of the hauling configuration PDM Bridge's customer at the Toledo, OH bridge site was initially skeptical about PSTC's ability to access their designated lifting area by backing in. With delivery of the first girder, however, their concerns were allayed. PSTC's deliveries arrived from Wisconsin as fast as the erector could receive them. Once unloaded, Perkins'operators immediately reconfigured their transporters for the two-day return trip by shortening each transporter by 18 feet and narrowing it from the loaded 16 feet width down to 14 feet. Each of the super-loads had a six-day cycle time, much quicker than would have been possible with old-style hauling configurations comprising house-moving dollies.