BRIDGE GIRDER INSTALLATION ENGINEERING

Scope of Work description:

Lowther-Rolton (L-R) was engaged by Walsh Construction to provide the transport, jacking, and lift engineering for the installation of two sets of bridge girder pairs for a new bridge to be constructed in Gary, Indiana. Each girder pair was 175’ long, 10’ wide, 6’ tall, weighing 135,000 pounds. 

The bridge location dictated that the girder pairs had to be moved under the existing I-90 Indiana Toll Way bridge before being launched over the Grand Calumet River. 

L-R’s in-house engineers prepared a drawing and calculation package for the operation. The girders were then installed using a Manitowoc MLC300 crane in tandem with SPMTs fitted with a rear launching frame. 

Based on site documentation and details of the new bridge girders, the detailed drawings and calculations were prepared to illustrate each and every step of the plan. 

Acting as an extension to the established Walsh team and the appointed equipment suppliers L-R ensured that the components making up the cranes, transporter, and rear launching frame and their connections were sized, designed, and deployed correctly based on the calculated load share. 

Together with the bridge design engineers it was determined how far the girder pairs could be cantilevered from the SPMT at the North side, to then determine the required initial lift radius the MLC 300 positioned to the South of the river. 

The girder pairs were assembled on stacks of wooden crane mats at a pre-set elevation which allowed the two 6 line SPMT trailers to self load using trailer hydraulics. The girders were first moved into position across the river by SPMT. Then the weight of the girder pairs was shared between SPMT and crane, and the SPMTs continued to move the girder pairs towards the North abutment wall while the crane radius was decreased. 

The SPMTs and crane lowered the girder pairs as close to the final location as possible, followed by a jacking operation to gradually remove the crane mats from the deck of the trailer, and then climbing jacks were used for the final lowering of the bridge onto the bearings. The MLC350 crane continued to hold the weight of the south end of the girder pairs, until that end was also resting on its bearings. 

The two girder pairs were installed by the team in a safe, efficient, and incident free operation over 3 day shifts, with the day between installations being to reconfigure and prepare the second girder pair.