Leading engineering consultancy, AV Technology (AVT) has successfully assisted with the critical lifting stage of an essential upgrade project for the world famous clipper ship, the Cutty Sark.
The consultancy was contracted by SH Structures Ltd, who were responsible for the design, manufacture and installation of the steel temporary lifting cradle, and for the detailing, manufacture and installation of the strengthening steelwork which had been designed by Buro Happold.
The work has been crucial to the conservation project, which includes raising the ship by three metres to build a permanent visitors centre underneath. This historic clipper is based in Greenwich and is due to be reopened by the Queen next year as part of her Diamond Jubilee celebrations.
AVT provided specialist instrumentation to measure and monitor the structural integrity of the Cutty Sark during the critical lifting phase and subsequently during the next six months of restoration. The monitoring system enables AVT to gather vital data on the load distribution within the 280-foot structure, to ensure that the ship’s structure was not subjected to high stresses at critical points during lifting and to ensure the long term stability of the ship’s frame and supporting props
The AVT team, led by Neil Parkinson and Simon Hirst, installed a strain monitoring system consisting of 96 strain sensors to monitor loads in the ships metal frame and the supporting props and tie rods that hold up the 800-tonne weight of the ship. The project had to meet tight deadlines as everything needed to be in place before the ship was raised vertically by three metres from its original position of sitting on its keel on the bottom of a dry berth.
To provide continuous monitoring of the vital loads, AVT supplied a PC based data logging system with real-time displays of loads in all critical locations and with automatic alarm settings to provide text message alerts if any of the loads exceed pre-set alarm thresholds.
During the lift process it was crucial that the structural engineers had live access to the load data for analysis and therefore AVT used wireless technology to transfer data from the datalogger on the ship to the real-time display on a PC in the control room. The data was easily exported into Excel for further detailed analyses before the lifting jacks were incremented.
Although the lifting work is complete, AVT will continue to monitor the Cutty Sark as it prepares for reopening in 2012.
Neil Parkinson, AVT’s Technical Director said: “The commissioning of a reliable instrumentation system to provide real-time monitoring of load levels in critical areas was a critical part of the lifting operation, enabling the jacking process to be properly controlled to ensure that structure of the ship was not damaged and that the operation remained stable.”
Simon Hirst, AVT’s Special Projects Deputy Manager continued: “There is still a lot of internal and external work to be done in preparation for the Cutty Sark becoming a visitor attraction. The new position of the ship will allow people to walk underneath when opened. The ongoing monitoring is intended primarily to ensure the stability of the ship in its raised position and to verify the integrity of the supporting props as more of the original fabric of the ship is reinstalled including the main mast and woodwork.
Strain monitoring is a proven and reliable method for assessing the performance of a structure and is a key area of expertise for AVT, who has performed structural monitoring for over 35 years on many projects including nuclear power stations, bridges, offshore structures, industrial vehicles and buildings.