Linkspan installation, India
ALE has successfully installed one of the world’s longest linkspan bridges in Gujarat, India. This was the first time ALE’s hydraulic floatover jacks were used.
The linkspan bridge, weighing 950t and measuring 100m long, required extensive retrofitting as it was designed for lifting by crane not jacking. ALE designed a jacking bracket, to transfer the jacking forces into the linkspan so the bridge could be positioned at an incline of up to 5.5° to match the difference of elevation of the jetty and floating pontoon, as well as a spreader mat system to transfer the loads onto the barge.
The linkspan bridge was manoeuvred on the barge from its standby position and moored at the installation location using six 20t mooring winches.
ALE utilised four floatover jacks, specially designed to overcome the huge 10.33m tidal variation, to lift and lower at high tide.
ALE provided the ballast, stability and strength calculations, executing the ballasting and de-ballasting using a 250cu/hr deck pump ballast system of the barge.
During the operation, ALE had to negotiate the strong currents of The Gulf of Cambay. ALE had used a compact tide monitoring system to check the actual and predicted tide data in Gogha, and selected a date to maximise the slack tide time. With an installation pocket of just 1m gap, ALE synchronised the ballasting to increase the draft with the rising tide and compensate for the weight transfer from the barge during jacking.
The barge was then removed from under the bridge in low tide using two 20t tugs.
ALE managed to complete the set-up within the tight timeframe set by the local maritime board. The bridge was installed within the tide window of approximately three hours.