Falls Creek Bridge

Following the devastating 2021 Atmospheric River event, the existing Falls Creek Bridge was washed out, severing a critical transportation link. KWH Constructors was first mobilized to restore access quickly by installing a temporary Acrow bridge to maintain traffic flow while the permanent replacement structure was constructed. The temporary bridge was installed from the north side using a single 500-tonne Liebherr crane, allowing traffic to be restored rapidly while permanent replacement work proceeded.

The new Falls Creek Bridge is a 79 metre long steel plate girder bridge consisting of four girders set on a 780 metre horizontal curve. The 9.5-foot-deep girders presented unique erection challenges due to the bridge curvature and restricted site conditions.

KWH executed a specialized partial launch erection method to safely install the bridge. Temporary rollers were positioned on a falsework bent constructed just ahead of the south abutment, allowing the girders to be incrementally launched across the span. To balance the structure during launching operations, precast concrete counterweights were mounted on top of the girders at the south end, while a 40-foot-long steel nose girder was attached to the north end to reduce cantilever forces during advancement.

The bridge was launched in pairs of girders at a time. Once the advancing girders extended far enough across the span, a 700-tonne Liebherr crane positioned at the north abutment connected to the nose girder to assist with the final stage of erection. The launching operation proceeded successfully without requiring a second assisting crane, allowing the counterweight system at the south end to remain in place throughout the final positioning operation.

Following steel erection, KWH installed the precast concrete deck panels to complete the bridge structure. Once the permanent bridge was opened to traffic, the temporary Acrow bridge was dismantled and removed from the site.