Location: UK | Year: 2009 | Size: 35m diameter
Overview
The project involved the design, construction and installation of a 35m (115ft) diameter, inflatable dome to serve as the venue for the inauguration ceremony for the South Hook Liquid Natural Gas (LNG) terminal at Milford Haven in South Wales, UK. The dome is the largest structure of is kind ever constructed.
The terminal, the largest of its kind in Europe, is a joint venture between Qatar Petroleum, ExxonMobil and Total. It forms part of the Qatargas 2 project which is the world’s first fully integrated LNG supply chain. LNG from Qatar travels from its origin in the Arabian Gulf through the Red Sea and Suez Canal to its destination in the deep water harbour at Milford Haven in a fleet of dedicated LNG ships.
In April, 2009 a huge event was held in Qatar to commemorate the departure of the first of the LNG ships headed for South Wales. The project involved a similar event in Milford Haven to celebrate the arrival of the ship and the inauguration of the South Hook LNG terminal.
The inauguration ceremony was attended by three members of the British royal family, Her Majesty the Queen, the Duke of Edinburgh and Prince Andrew in addition to three members of the Qatari royal family, the Emir of Qatar, Sheikh Hamad bin Khalifa Al-Thani, Sheikha Mozah Bint Nasser Al-Missned, and Sheikha Hind Bint Hamad Al-Thani.
The BriefThe inauguration event was created by our client, WRG Creative Communication. They required a 35m hemispherical dome to form the venue for the event which would include speeches by her majesty the Queen and the Emir of Qatar together with an audio visual presentation of the Qatargas 2 project and performances from various British and Qatarti music and dance artists.
The dome would be surrounded by aluminium framed marquees which would house reception areas and exhibition spaces. The entire complex would be installed on a temporary deck located in the contractor's car park at the South Hook terminal.
The time available to install the deck, marquees and dome was extremely limited and did not allow sufficient time to erect a dome with a rigid framework. The time available to install the dome was just two days.
The site for the event was an exposed location on the South Wales coast with a reputation for high winds. One of the primary concerns of the client about using an inflatable dome of such a large size was its structural performance, particularly in high winds. We were selected to supply the dome because of our assurances that our high-pressure welded inflatable structures could provide the necessary performance.
The client also required that the dome would block out 100% of the natural light so that the interior lighting and visual presentations would have maximum impact. Noise levels from the pressurisation system were also a concern.
Our SolutionIn addition to the sheer size of the dome, it was also to be installed on temporary decking on a site with a significant slope.
The deck measured 63 metres (207 feet) by 61 metres (200 feet) and was not designed to withstand heavy plant such as forklift trucks and cranes. The dome therefore had to be capable of being installed using manpower alone.
The solution was to design the dome to be supplied in five pieces, each weighing around 650kg (1430 lbs). Each section was lifted from the delivery truck onto the edge of the deck using a forklift truck from where it was dragged into its final position by hand.
A totally new method of joining the sections of the dome on site had to be devised. The method not only had be structurally sound and weatherproof, but invisible so that the assembled dome looked like one continuous structure. The solution was to use two layers of fabric keder which were stitched and heat sealed to the dome. The fabric keder strips on adjacent dome sections were then joined using aluminium keder track cut into sections to follow the curvature of the dome. A separate fabric weather strip was concealed between the two layers of keder to provide additional weatherproofing.
Safety is always of paramount importance especially on structures of this size. In addition to simplifying the installation, the decision to design the dome in five sections was also taken in order to provide five independent pressurized zones, each with its own pressure control system. In the unlikely event of a failure of one of the sections, the remaining sections are more than capable of supporting the failed section and preventing the collapse of the dome. This arrangement was tested successfully on the full scale dome before delivery.
The OutcomeThe inauguration event was a total success. Despite windy conditions throughout the installation and during the event itself, the dome performed flawlessly.
We spent a great deal of time during the design phase of the project analysing the structural performance of the dome. This involved developing new procedures for using finite element analysis for predicting the stresses present in inflatable structures and their deflections under various loads. The procedures were validated during the design phase by testing small-scale prototypes of sections of the dome. Measurements were taken of the dome following its installation which showed that its deflection in high winds was exactly as predicted.
Since the dome used our unique welded construction, it required very little air to maintain pressure once inflated. The low volume of air consumption meant that the noise levels of the pressurisation system were inaudible to those attending the inauguration.
The dome was delivered on time and installed in just 15 hours by a small crew with no cranes.
