Puyallup River Bridge Demolition

Coffman provided structural engineering for the demolition of two existing 16-span bridges, No. 5/456 E&W, carrying I-5 over the Puyallup River in Tacoma, Washington. The demolition contractor was unable to use a barge crane located in the river, so it was determined that the existing precast concrete girders would be lifted from above using a custom-built beam mover system (BMS). The BMS was supported by the existing girders in the adjacent bridge span.

During demolition, the contractor elected to remove two 100-foot girders at a time with each load weighing up to 300,000 pounds. The existing girders, deck, and bridge substructure were checked for the large wheel load reactions from the BMS including a 3D analysis model to study the effects of the bridge skew on the wheel load distribution.

Coffman also assisted with the structural analysis for the BMS to optimize wheel load locations and minimize the number of wheels on the BMS to enhance maneuverability. The anchorage, rigging, and spreader beams were also designed for each lift to limit the tensile stresses in the top flange of the girders being lifted.

Coffman’s unique combination of experience with structural engineering, bridge engineering, and industrial design, allowed us to partner with the contractor for a safe and efficient bridge demolition solution.