Gantry lift for railroad bridge

The construction of the bridge as two spans per rail line meant that a single span could be changed during a single 50 hour weekend work block. Each span section weighed 400t and was 100ft long, 12–17ft wide and 9ft high.

Western Mechanical opted to use its new Enerpac SBL1100 telescopic hydraulic gantry rather than a crane for the project. “Using a crane would have been expensive especially since all work on the bridge was carried out over eight weekends,” said Rob Doucet, project manager for the heavy lift division of Western Mechanical.

The challenge was to lift the old bridge span clear of the bridge and then install the new span without placing any excessive load on the partly deconstructed bridge. To achieve this, the company installed its deep truss gantry track system running parallel to the bridge and on either side, but independent of the bridge itself. This approach relied on using a gantry header beam that was wider than the width of the bridge, in this case 24m in length. There were also modifications made to the swivel interface where the header beam rests on the top of each gantry leg.

With the gantry in place, Western Mechanical could begin the job of removing the span sections. Doucet said: “The telescopic legs meant we had the vertical movement to lift the span section clear of the bridge itself. The gantry’s independent track system running the length of the bridge gave us east-to-west movement parallel to the bridge providing us the ability to utilise Enerpac’s independent motorised gantry leg rollers saving time to reset for the next adjacent span lift. An integral component to the system was the Enerpac header beam and powered side shift beam traveller units. With a 1,500kN capacity these units allowed us to move the lifted span from north-to-south perpendicular to the tracks and onto awaiting rail flatcars to be loaded out to the demolition yard. The process was reversed for installing the new spans.”

An important safety feature was the ability to mechanically lock the header beam and gantry legs in place, allowing rail clearance for train traffic to flow beneath during the week.