Pop up Singapore hangar built in just eight hours

Mott MacDonald modelled a prefabricated stressed steel arch solution in BIM to assure integrity and cut work at height. 

Swiss-based aircraft charter and engineering company Jet Aviation wanted to upgrade its maintenance facilities at Singapore’s Seletar Airport which caters for private jets. Mott MacDonald was appointed by architect Lu & Wo to undertake detailed design of a hangar, workshops, offices and associated systems as part of a new 5000sq m facility that would also need to incorporate the existing structure.

“The hangar features a swooping roofline that creates a seamless connection between the old and the new,” explains Mott MacDonald project manager Greg Cox. “The new structure triples existing capacity, meets maintenance requirements for Boeing, Bombardier, Gulfstream and Nextant aircraft, and majors on operational efficiency, buildability and visual flair.”


For speed, the stressed steel arch from contractor ASI was selected. Using this system, prefabricated steel structural truss sections are assembled on the ground. Pin joints connect elements that make up each arch ‘rib’ – one end of each rib is anchored; the other is mounted on rails. Steel tendons are then fed through the bottom chord of the trusses and pulled taut by hydraulic jacks.

This pulls the rail-mounted ends inwards and forces the centre upwards, ‘popping’ the arch into shape in just eight hours. “Using the stressed arch method, services could be installed in the prefabricated structure at ground level, including lighting and the fire deluge system,” Cox explains.

“This cut the safety risks and time involved in working at height – the arch is 25m at its tallest, around seven storeys high.” Fitting out all services prior to erection, and the erection method itself, allowed the overall programme to be reduced by two thirds compared to conventional approaches, and has created an arch with an internal clear span of 100m.


BIM is standard for Mott MacDonald’s large technical projects and it is also becoming compulsory for government submissions in Singapore. However, setting up the detailed models can be time intensive, and neither the architect nor owner had fully exploited the benefits of BIM on a project before.

“Once our client was convinced of the benefits that the technology would offer, we worked together to use BIM to model the piles and foundations, the entire stressed arch and all installed systems”  - Greg Cox

To build confidence in the technology, the consultant explained how implementing a BIM-first approach would yield many benefits, including the ability to share comprehensive information in real time with partners around the globe.

“Once our client was convinced of the benefits that the technology would offer, we worked together to use BIM to model the piles and foundations, the entire stressed arch and all installed systems,” says Cox.

A 10 zone deluge system capable of discharging 1600cu m of foam per hour provides a vital line of defence against fire, a very real risk with part-fuelled aircraft entering the hangar. “We used the BIM model to undertake geometric and hydraulic analysis of the fire deluge system, and to simulate emergency scenarios to demonstrate how well it would work,” he says.

“BIM also helped us to hide the pipework connecting the hangar fire system to the foam tanks located at the rear of the site, to retain the clean, clutter-free appearance important to the architectural concept.”

In the event of fire, regulations require the discharged foam to be contained to avoid contamination of the environment and sewer system. Typically this requires large underground tanks to collect the foam, which are expensive to build. Instead, the aprons were designed to act as containment structures: if discharged, the foam will be physically unable to spread past the apron boundaries, and rainwater drains will automatically close to stop foam entering the sewers. This solution cut costs while meeting local regulations.


Maintenance hangars include ‘ground pits’ – structures that contain specialised components needed during servicing, such as power supplies and compressed air. These are set into the hangar floor. Pits are usually supplied as complete units but, on this project, the components were purchased separately and the casings were built on site.

“We worked closely with Jet Aviation’s selected supplier Cavotec to model every component and import them into the BIM model, to ensure that the parts would all fit,” Cox says. “Using the model to simulate maintenance operations, we reconfigured the layout of the ground pits and added service trenches around the perimeter: by doing so, we reduced the number of ground pits from eight to two. This cut cost without compromising capacity.”


The use of BIM enabled information to be easily shared between the project’s multiple partners across the globe. The Mott MacDonald lead team in Singapore liaised with our offices in London for fire system design and called upon its North American infrastructure business, Hatch Mott MacDonald, for peer review. The consultant helped facilitate strong communication with Jet Aviation, based in Switzerland; stressed arch designer ASI in Australia; main contractor Holmes Construction from New Zealand; and Cavotec, the German manufacturer of ground pit components.

“By working closely with Mott MacDonald, we’ve been able to draw upon the company’s wealth of experience to develop a comprehensive BIM model that fully integrates the engineering solutions needed to achieve Jet Aviation’s objectives,” concludes Lu & Wo director Tang Sau Kit. “Together, we’ve used the sophisticated technology to realise significant and lasting value for our client.”


Ground pits contain specialist equipment needed for servicing aircraft. Virtual units were created in a BIM environment and used to simulate maintenance operations. In doing so it was found that, by reconfiguring their placement, the total number of units could be reduced from eight to two, saving cost.

Greg Cox is Mott MacDonald M&E director, Singapore