The structures and equipment for the steel crown’s strand jacking weighed 830t – equivalent to 600 saloon cars
The crown of the Al Wasl dome, set to be one of the main highlights of the Expo 2020 Dubai site, has been put into place after an intricate and complex construction operation that took months to plan and implement.
The 130-metre-wide domed steel trellis which now encircles Al Wasl Plaza occupies 724,000 cubic metres and stands 67.5 metres tall – higher than the Leaning Tower of Pisa. During Expo 2020 Dubai, the dome will be the largest 360-degree projection surface in the world.
“The crowning of the Al Wasl dome is a significant landmark not just for Expo 2020 Dubai but for the whole of Dubai and the UAE,” said His Highness Sheikh Ahmed Bin Saeed Al Maktoum, Chairman of the Expo Dubai 2020 Higher Committee, President, Dubai Civil Aviation Authority, Chairman, Dubai Airports, Chairman and Chief Executive, Emirates Airline and Group. “This new architectural marvel joins a long list of inspiring designs that our country has created through collaboration, sheer hard work and the unending, ambitious vision of our leadership and people. It is another example of what the nation can do when it combines all its talents to such formidable purpose.”
His Highness Sheikh Ahmed added: “Al Wasl dome will take a lasting place at the very summit of our country’s world-renowned architectural achievements. My heartfelt congratulations go to everyone involved in successfully completing this amazing engineering feat.”
Preparation for the Al Wasl dome’s crowning first began in June 2018 when the final pieces of the dome’s steel trellising left Italy. Individual elements arrived in Dubai in a month later and the assembly of the prefabricated crown could begin at ground level ahead of being raised into place via strand jacking.
On-site technicians had to use specialist lifting equipment and was a “unique engineering challenge,” said Ahmed Al Khatib, Chief Development and Delivery Officer, Expo 2020 Dubai: “It was the most exhilarating day of my entire career. We had one chance to get this right.”
The Al Wasl dome weighs a total of 550t and the strand-jacking operation to lift the 22.5m crown in place on top of the vertical trellis which was sitting 45m above the ground required precise positioning. With a margin of error of only 3mm, 18 hydraulic jacks – aided by steel lifting ropes connected to 18 freestanding temporary columns – slowly raised the curved steel crown.
It was then attached using 53 temporary connection brackets. 800 engineers and construction technicians had to use GPS indicators throughout to ensure perfect alignment and carefully monitor every millimetre of the process through the night.
A series of tension cables were installed to retain the geometry of the trellis structure as it was lifted and finally connected to a central temporary compression ring.
This process required multiple test lifts to measure the movement of the structure as it was lifted off the ground. Tensioned cables were further adjusted until the trellis perimeter connection points were in the positions required for the full lift to commence.
Now positioned, the final piece of Al Wasl dome will be welded to the rest of the trellis, a process that will take 25 days to complete.
“Crowning Al Wasl Dome was both incredibly exciting and one of the most challenging engineering operations in the world,” said Ahmed Al Khatib. “Lifting such a large and heavy structure involved a huge number of variables. Something as simple as a shift in direction of the wind or change in air temperature could have had a big impact on our calculations, so constant monitoring and reassessment was essential throughout the process.”