Denzai Engineering Corporation has used an Enerpac JS-250 jack-up system for a bridge removal project in Narita City, Chiba, Japan. The 150-t overpass road bridge was removed as part of the preliminary work ahead of a planned runway extension at Narita International Airport. Deploying the JS-250 towers, mounted on self-propelled modular transporters (SPMTs), allowed the bridge removal overnight, minimising traffic disruption on the busy Higashi-Kanto Expressway.
The extension of Runway B at Narita International Airport requires the creation of a new grade-separated intersection between the Higashi-Kanto Expressway and the extended section of Runway B. Removal of the bridge will allow the Higashi-Kanto Expressway to be temporarily rerouted during the intersection construction.
Lack of space prevented the use of a crane for the bridge removal and so Denzai opted for the JS-250 jack up system due to its lifting capacity, stability and compactness. Two JS-250 towers were mounted on each of two SPMTs and a steel support platform placed on top. The platform was used to support the 21-m-long, 5-m-wide bridge deck as it was lifted and transported to a rigging location near the expressway. The project was carried out in June this year.
The Enerpac JS-series jack-up system is a multi-point lifting system comprising four jack-up towers, one positioned under each corner of a load. The lifting frame of each jack-up tower contains four hydraulic cylinders, which lift and stack steel barrels. The load is lifted in increments as barrels are inserted via an automated system and stacked, forming the lifting towers. Managed by a single operator, each tower’s lifting and lowering operations occur simultaneously, while the jack-up’s synchronous technology maintains the balance of the load.