MLX MacKay River Bridge

The Mildred Lake Extension project (MLX) involves a bridge construction over the MacKay River, providing access to a mine. The general contractor, Graham, constructed a three-span structure with a span arrangement of 35m - 45m -35m, and a 45m wide deck for heavy mining trucks. Spannovation’s scope included erection procedures and staging analysis, design of stability bracings and wind restraints, girder transport & storage. About 2700 tonnes of structural steel were erected across 18 girder lines.

Erection Methodology:  A 300-ton crawler hoisted south side segments from the south abutment to field splice 3. An 825-ton Manitowoc erected the North Segments from Field Splice 3 to the north abutment. Erection started from the south and concluded at the north. It began with the middle two girder lines to engage the central shear key as the transverse restraint. The process progressed northward from field splice 3 to the north abutment. The first girder line needed top flange bracing and a transverse restraint until it could form a stable unit with the second girder line. Longitudinal restraint was realized by welding the girder at the south pier to the bearings.

Challenges Addressed: The high number of girder lines necessitated precise accounting for wind shielding effects. Creative wind management, using monitored and short erection windows, was implemented to minimize demands and optimize temporary works. Stability was ensured for the partially erected structure at all stages, including the long 12m cantilevers for 1 in 10-year wind demands. The storage bed was engineered to facilitate segment splicing. It features the capability to remove girder lines, while maintaining the stability of the remaining lines independently with chains and push-props.