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ISG races three ships in delivering Liverpool’s dockside exhibition centre

Contractor has an unusual deadline to deliver the latest addition to the maritime heritage of Liverpool on the city’s famous dockside.

Project: Exhibition Centre Liverpool and Pullman Hotel
Client: Liverpool City Council
Contract value: £66m
Contract type: Design and build
Region: North-west
Main contractor: ISG
Steelwork subcontractor: Billington Structures
Concrete frame subcontractor: Heyrod Construction
Piling subcontractor: Bachy Soletanche
M&E subcontractor: Briggs and Forrester
Structural engineer: Booth King Partnership
Start date: May 2012
Completion date: August 2015

Down on Liverpool’s waterfront, the quays of which helped build this great port, stand Liverpool’s ‘Three Graces’ – the Royal Liver Building, Cunard Building and Port of Liverpool Building.

They stand testament to the port’s prowess as an international centre of trade and commerce.

Further upstream along the east bank of the River Mersey lies the famous Albert Dock complex.

Once home to a host of bonded warehouses, the area now boasts the Echo Arena and BT Convention Centre.

Within this complex, ISG is building the latest stage of the waterfront’s redevelopment: a new four-star hotel and exhibition centre.

“We only dip into the water table. We brought ourselves out of it through the design – why wouldn’t we?”

Project director Frank Joyce is driving the scheme for the contractor and as a proud Liverpudlian understands its importance to the city.

“I want Liverpool to be as successful as possible,” he says. “The development of the Arena and Convention Centre has benefitted the city enormously.

“The addition of the ECL exhibition centre and new Pullman Hotel will only expand that.”

Funded through client Liverpool City Council with input from the local authority’s arena operating arm and end user ACC, the £66m project will see the new ECL and hotel open for business on contract completion in summer 2015.

However, an unofficial, rather more pressing date has been handed to the project team – 25 May 2015.

On that day, to celebrate the 175th anniversary of Liverpool-based Cunard Line, its three enormous liners – the Queen Elizabeth, Queen Victoria and flagship Queen Mary 2 – will tie up alongside the development on the city’s waterfront.

True design and build

For the time being, the site is a hive of organised endeavour and Mr Joyce seems relaxed about the project delivery schedule.

Part of this is probably down to the fact this is a design and build contract in the truest sense (see box). It is not a ‘design and dump’ scheme – where the design is taken to such a point that the contractor has no bearing on it, other than picking up associated risks with someone else’s drawing board musings.

Appointed as main contractor following a two-stage tender process, the team started on the site under an enabling works contract in May 2012. The value of this package alone was more than £6m.

“There was a lot of work carried out in that part of the scheme,” Mr Joyce explains.

“We reached an agreement with the client that we would carry out the service diversions, unexploded ordnance surveys and piling work. The client also agreed to commit to procurement of the steelwork under this phase.”

Dockside ground engineering

Ground across the site is a mixture of riverbed sands, which were dredged from the Mersey and used to fill the original docks during the 1980s, and crushed fill from the demolition of warehouses during this period.

Specialist contractor Bachy Soletanche carried out a piling regime, installing 450 to 600 mm-diameter CFA piles, stretching 20 m to the underlying sandstone beds with a 1.5 m socket.

In a departure from the original plan, piling beneath the main exhibition hall floor was rejected in favour of cement stabilisation (see box) under a value engineering drive.

Mr Joyce says: “We were advised by the structural engineer that the piles could be replaced beneath the slab of the main hall with cement stabilised ground.

“We had gleaned such an understanding of the site conditions during the enabling works package that we were more than happy to go with that solution.”

Engineering out the risk

A 2.5 m-deep and 2.5 m-wide service tunnel runs through the centre of the main hall, branched off with various services contained in precast concrete channels.

“By using waterproof concrete we have engineered out the risk. We knew we would be creating a finished surface and we didn’t want to have to come back”

Frank Joyce, ISG

Constructed on site from 250 mm-thick waterproof concrete, the tunnel sits just below the water table. It features a cast insitu reinforced concrete capping slab, which will become part of the finished slab when the rest is raised to level.

Mr Joyce adds: “By using waterproof concrete we have engineered out the risk. We knew we would be creating a finished surface and we didn’t want to have to come back.

“We only dip into the water table. We brought ourselves out of it through the design – why wouldn’t we?”

The steel-framed exhibition centre features roof trusses that span 45 m and typically weigh 16 tonnes. These are fabricated in three 15 m sections and spliced together on site – being lifted by two 60-tonne crawler cranes.

The nine-storey, 658-room hotel is clad using a rainscreen system and glazing elements to create the effect of three double-storey tubes lying on top of one another.

The added planning restriction was that the top of the hotel can be no higher than the city’s Anglican Cathedral ‘shoulders’, when viewed from across the River Mersey.

Design scope widened

It is being built using post-tensioned concrete, and was added to ISG’s scope of works at a later stage than the exhibition centre.

“We went with post-tensioning because it offered us a surety in the construction process”

Frank Joyce, ISG

“We went with post-tensioning because it offered us a surety in the construction process. We reviewed precast concrete but elected to go down the post-tensioned route because we needed a quick answer,” Mr Joyce says.

With 200 mm thick concrete blade walls and 300 mm thick slabs throughout the building, the two tower cranes being used on the scheme have been kept busy, skipping concrete into position for the pours.

With less than a year to go before Cunard’s ‘Three Queens’ line up on the Mersey, it looks like Liverpool’s waterfront will be able to boast a more permanent but equally impressive addition.

Contract drives overall success

All too often contractors are stifled by onerous design conditions imposed on them through the artificial use of the ‘design and build’ contract.

They are obliged to take on designs that are so well evolved they offer little or no chance for the contractor to make any gain. Little more than an opportunity for the client and designer to offload risk, they have become known as ‘design and dump’ contracts.

Here in Liverpool, the team has been fortunate that the contract has been let as a D&B in the truest sense.

With a long lead-in time of more than 12 months, ISG first became involved in the ECL scheme in 2012 under a two-stage tender process – which included the responsibility of pushing the scheme through the planning permission stages.

Liverpool City Council was also sensible enough to clear a large enabling works contract that included the advance purchase of the structural steel.

“We were able to develop the design at the same time as the cost developed, so we were able to keep a close eye on all aspects. We were able to really drive the project forward,” Mr Joyce says.

“We take on more responsibility, but ultimately everyone gets a better product. The client had the foresight to agree to the enabling works contract before the main contract had been officially signed.

“That allowed us and the steel work contractor to really hit the ground running. The steel was coming out of the ground within a couple of months of the contract being signed in December 2013.”

 

Exhibition of cement stabilisation

With the whole team focused on carrying out a value engineering exercise, it was representatives of the structural engineer Booth King that suggested omitting the piles beneath the slab of the main exhibition space – instead, treating the ground using cement stabilisation techniques and laying the main slab directly on top.

With the bulk of the ground across the site being made up from dredged river sands and fill, there was little pre-cement treatment required. A little crushing and sorting on site meant the team used all but the smallest amount of excavated ground during the cement treatment.

“We were lucky that the ground was so suitable for treatment. We had learnt a lot about the ground conditions during the enabling work, so we were confident the cement stabilisation would work,” Mr Joyce says.

Cement was mixed at a 5 per cent concentration with the sifted and chemically tested earth, before being placed in layers and compacted to depths of 500 to 750 mm, forming a solid formation layer for the concrete slab.

“It was a fantastic solution,” he says. “If we had a little more time, perhaps we would’ve been able to use the same treatment beneath the hotel.”

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