This five span bridge at Ashcroft, BC replaces a sixty year old truss structure. The installation of the new 783 foot (238m) long bridge posed an erection problem as the Thompson River becomes a torrent during run off.
We chose to launch the steel trapezoidal bathtub girders from both sides, closing in the middle. The bridge was launched over a roller system that KWH/Somerset Engineering designed to minimize the critical web buckling stresses. The rollers were mounted on rocker beams which also simplified passage of plate thickness changes. Somerset designed a falsework bent, an expandable spreader bar lifting system and a launching nose. An innovative hydraulic push-grip mechanism was conceived to replace the pulling hoist and reeving operation which is conventionally used. Later a scheme to dismantle the old bridge was engineered and the truss was removed from the centre back, piece by piece