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Transport: T2B is the tip of the iceberg

Terminal 2B, Heathrow Airport’s biggest ever airside project, was completed on time this month, with off-site modularisation and building information modelling key to its success. But there is more beneath the surface than meets the eye.

United Airlines flight 958 from Chicago to London arrived on schedule at 05.55 last Tuesday, marking the operational opening of Heathrow’s stunning new Terminal 2 - also completed on time. A key component is Terminal 2B (T2B), the satellite pier through which passengers embark and disembark.

T2B is big - much larger underground than it is above the surface - and constituted a major civil engineering challenge. It is the largest project ever undertaken airside at Heathrow. Every worker, every piece of plant, every delivery of material required security clearance, making programming even more complex than usual. And the structure required innumerable design briefs, with 30 or more major stakeholders holding substantial interests.

Extensive use of off-site modularisation and leading edge building information modelling (BIM) were prime reasons why T2B contractor Balfour Beatty was able to make a success of its £590M building project. No surprise, then, that the firm has just been appointed one of four contractors to carry out the airport’s £1.5bn programme of works over the next five years.

“We have a long history of working for client Heathrow Airport (HAL) and its predecessors since the early ’90s,” says Balfour Beatty Construction Services aviation director John Keaveney. “We were the second biggest contractor on Terminal 5 and were well placed to give T2B a good go.”

And give it a good go Balfour Beatty did. Built to serve 10M long haul passengers arriving and departing every year, the satellite pier is a 522m long three-story building, much of it clad floor to ceiling in glass, boasting an impressive interior.  

John Keaveney Balfour Beatty

“Future-proofing is a significant proportion of the work we’ve carried out, with enormous basements safeguarding areas for future baggage systems and a track transit system”

John Keaveney, Balfour Beatty

 

 

 

 

 

 

 

In total, 16 long haul stands are serviced, 10 of which can take Airbus A380s.

But as Keaveney says, the building is like the tip of an iceberg. “Most of our activity has been underground,” he explains. “Future-proofing represents a significant proportion of the work we’ve carried out, with enormous basements under T2B effectively safeguarding areas for future baggage systems and a track transit system.”

Future-proofing Terminal 2

Terminal 2B cross section

Terminal 2B cross section

Terminal 2’s official name is The Queen’s Terminal, and the Queen will officially open T2 later this month - near to where she opened the structure’s predecessor in 1955.

That terminal, named The Europa Building, handled 1.2M passengers in its first year - a fraction of the 8M passing through in 2009 before it closed for demolition.

The new T2 is made up of a principal building (T2A), built by a Ferrovial/Laing O’Rourke joint venture, and the pier building (T2B), built by Balfour Beatty.

The outline design for the £2.5bn main building was carried out by Foster + Partners, before Spanish architect Luis Vidal + Architects took it on for detailed design.

It includes an undulating steel framed roof that floods the building with natural light, according to client HAL.

“The objective for Terminal 2 was to create a space that would be a destination in itself,” the company says.

The Grimshaw Architects-designed T2B satellite pier (above) is linked to T2A via a passenger tunnel under the airfield.

T2 will be home to 23 Star Alliance airlines, as well as Aer Lingus, Virgin Atlantic Little Red and Germanwings.

Its design is “future proof”, with the structure ready to accommodate facilities being extended by further development.

For example, the satellite pier has safeguarded areas beneath the surface for baggage handling and a track transit system to reach T2C, a future satellite pier.

Heathrow’s T1, still in full operation, will close in 2016 to eventually make way for an extended T2A.

HAL is thinking ahead to a time when Heathrow might get its third runway.

Its recent revised plan to the Airports Commission proposes two main passenger terminals and transport hubs - Heathrow East (an extended T2) and Heathrow West (Terminals 5 and 6), connected by an underground passenger transit and baggage system.

 

T2B’s excavated volumes are equivalent in size to 250 Olympic swimming pools. Under the main pier, the basement is 360m long, 60m wide and 15m deep. The excavation for this, plus other subsurface space, meant sinking a diaphragm wall 2km long. Balfour Beatty Ground Engineering was the subcontractor for this.

In addition, 700 large diameter piles were needed, plus plunge piles.

The plunge piles meant the satellite pier’s north and south sections could be built using top down construction, which in turn meant an early start on the building’s superstructure.

For critical path reasons, involving underground plant rooms and a communications room, T2B’s centre section was built from the bottom up.

While this was going on, a two tier 250m long tunnel was created for passengers to travel between T2A (the main terminal building) and the satellite pier.

Balfour Beatty was involved with T2B from its very early stages, securing a design and build contract. One early decision was to opt for as much modularisation of services as possible. In the event, close to 550 modules were built off site for later transport to, and “plugging in” within, T2B’s burgeoning structure.

Keaveney says: “Off-site prefabrication meant a more efficient and safer way of delivering the building services packages on what was a complex project.”

Significant programme savings

The programme savings were significant, he claims. For example, a major mechanical plant room delivered to site in eight sections and installed in two weeks saved 24 weeks; and multi service risers were installed in one night, compared to a traditional approach, which would typically take six weeks.

Balfour Beatty Engineering Services’ manufacturing facility Modular Systems+ was involved in much of this, leading to an optimised building services design that lent itself to modularisation.

According to Keaveney, everyone knew the project was going to be highly complex: exchange of information, coordination and cooperation between all parties would be crucial; modularisation, in particular, would require perfect planning; just in time construction methods to overcome storage shortages on site were essential; and any disruption to the safe and efficient running of the airport was unthinkable.

“BIM has been huge on this project,” Keaveney says, explaining how Balfour Beatty got to grips with these and other issues.

“Working in close collaboration with HAL and our supply chain, our combined adoption of BIM from the early design stage has led to substantially increased efficiency and productivity, not least by allowing people to get together and visualise what they were going to be doing.”

He adds: “BIM has been particularly helpful on this job in making sure components fabricated off site can actually be manoeuvred into place and installed neatly on site.”

An example is the installation of two 100t air handling unit modules that involved all aspects of Balfour Beatty’s BIM implementation, ranging from 3D fabrication modelling in support of off-site construction to 4D construction planning simulations. Just in time methods were vital, and use of detailed 3D modelling, including associated conflict detection and resolution between design elements, allowed this.

Construction of T2B involved two phases. The first of which opened in two stages through 2009 and 2010 to provide six of the pier served stands, releasing land for the second phase, on which work began in October 2010.

Phase two involved much of the underground work and presented the most difficult challenges.

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