In Wales contractor Willmott Dixon is using advanced concrete techniques to outpace traditional methods.
Project: Computational Foundry
Client: Swansea University
Contract value: £21.4m
Contract type: NEC Option A – design and build
Main contractor: Willmott Dixon
Concrete subcontractor: Sterling Services
Steel frame subcontractor: Morgan’s of Usk
Piling subcontractor: Balfour Beatty Ground Engineering
Start date: June 2016
Completion date: September 2018
There was a time when students’ choice of higher education was largely based on a combination of teacher pressure, parental pushiness and, of course, exam results.
But now students are investing so much of their own cash into their futures, they are more inclined to pick exactly the right course, choose exactly the right university with exactly the right facilities for them, with less weight given to reputation.
This means universities must attract students through exemplar research facilities that are the envy of their competitors.
Education arms race
In south Wales, Swansea University has joined this education sector arms race with the addition of a new computational science centre at its developing Bay Campus to the east of the city.
The ‘Computational Foundry’, as the university’s head of college of science Matt Jones describes it, will benefit “not just Wales but the entire world”.
With such grand plans for the £31m facility, a Willmott Dixon project team is focused on bringing the scheme home ready for its first wave of research scientists and students in September 2018.
The team is using modern methods of construction to help it do just that, according to Willmott Dixon design manager Chris Townsend. “This is going to be an important building, not just for the university but for the rest of Wales. We want to deliver a flagship building that reflects its importance,” he says.
The contractor is working under an NEC Option A Design and Build contract and was brought in at Stage 3.
“It is predominately a brickwork façade with numerous layers and with various coursing techniques,” Mr Townsend says. “We looked at various construction techniques but in the end felt that by using precast concrete we could ensure quality and speed its delivery.”
“Traditional construction methods would have constituted an ambitious undertaking for even the most accomplished of brick layers”
Chris Townsend, Willmott Dixon
Mr Townsend cites the complexities of the building, such as the number of angles, bracketry and cavity trays necessary to form the complex reveals and overhangs on the façade, as another reason behind its precast concrete design. Fully coursed half-bricks set into the concrete will provide the final finish (see box).
“Traditional construction methods would have constituted an ambitious undertaking for even the most accomplished of brick layers,” he says. “We are working in an exposed coastal environment and being mindful of the shortage of skilled bricklayers within the industry at present, we thought opting for a site-built solution would have presented a significant risk to the project.”
The building is steel-framed and designed in two wings linked by a central atrium space. Each wing will feature four levels with a stair and lift core services each side of the building.
The east wing is surrounded by open plan collaborative workspaces which will replicate the ‘Google-esque’ offices that researchers and students in the computer science sector now aspire to, with support office space located around the atrium.
“Getting those connections designed correctly was laborious but vital”
Chris Townsend, Willmott Dixon
The west wing will feature two large lecture theatres on the ground floor, a move that has forced an increase in design height between ground-floor slab and the soffit of the first-floor slab to accommodate them.
The spirit of BIM
Willmott Dixon has long been an advocate of the advantages that BIM can offer, both for its own operations as well as for its clients and end-users. While it works to Level 2 across its business, here at the Computational Foundry scheme the client has decided not to take on the full BIM package.
Not that it matters much to the contractor’s site team. It is continuing to develop the project with full BIM capacity even if the client team fails to see the benefit beyond the virtual reality models.
“We are ‘working in the spirit of BIM’ here,” Mr Townsend says. “For us it’s standard practice and the client sees the benefit when we show the design models and VR mock-ups, but in terms of its FM legacy the client doesn’t see the gain. It already has its own FM systems in place and is confident in their suitability.”
“We did look at a precast frame, but steel was a better option for us,” Mr Townsend says. “We could get the co-ordination process done upfront to identify any restrictions. The precast system sits on top of a ground beam and is then bolted onto the frame. Getting those connections designed correctly was laborious but vital.”
Local supply chain
Beam spans across the inner frame hit 8 m with castellated steel beams being used to meet those larger spans. Specialist contractor Morgan’s of Usk fabricated and erected the steel. One of Willmott Dixon’s established supply chain partners, Morgan’s is based just east along the M4 corridor in south Wales – part of Willmott’s efforts to keep its suppliers as local as possible.
Despite being a steel-framed structure, the weight of the precast concrete cladding coupled with the nature of the ground conditions (the Bay Campus sits on a reclaimed transit site for oil giant BP) has seen the team use an array of precast concrete piles on which to found the building.
Piling specialist Balfour Beatty Ground Engineering used precast piles, which kept the noise down for neighbours and negated the chance of bringing up contaminated arisings.
“It has carried out most of the piling work on the Bay Campus site to date and it seemed logical to continue,” Mr Townsend says. “The piles were driven to refusal at around 6 or 7 m, which was shallower than we had anticipated. There must just be an anomaly in the bedrock at this point.”
The contract stipulates that the final building should hit a BREEAM Excellent environmental rating. Much of this is down to the airtightness and thermal efficiency values that a building constructed using precast panels can offer, but a photovoltaic array on the roof of the building’s east wing will boost its green credentials still further.
With the clock ticking on the Computational Foundry’s construction programme there is no time for the project team to rest up and Willmott Dixon is looking to get the final structure weatherproof so fit-out and finishing can begin.
Judging by the speed of construction so far, that September 2018 handover isn’t in any danger.
Pacey precast panels
Continuity and repetition is part of the attractiveness of any prefabricated construction system and precast concrete is no different. Across the Computational Foundry project there are 640 separate panels that are due to be installed, with just 10 variations amongst them.
The panels feature the fully coursed cut half-bricks that are set within 150 mm thick reinforced concrete panels at Taunton based architectural precast specialist Sterling Services’ casting yard.
Each of these bricks – an Ibstock yellow – are cut longitudinally into two. There are 250,000 bricks being used on this scheme - 500,000 half-bricks in total.
“They are all specially cut and are not slips,” Mr Townsend says. “Sterling Services went to Italy to find a machine that can automatically cut that number of bricks. Panel production is quite a simple system. The half-bricks are placed in plastic mould liners that allow the team to point them – a bucket handle finish – from the rear.
“Then the rebar cage with hooks and lifting eyes is positioned and the mould filled with standard precasting mix concrete. Any extras to the design such as bat boxes or mountings for CCTV systems can also be accommodated at this stage,” he adds.
The moulds can be stripped quickly with the panels stockpiled to cure, before being driven to site and hoisted into position directly from the delivery wagons using the mobile crane the team has in place. The final finish is a perfectly lined up brickwork façade that would have added to the project’s cost and delivery timescale if traditional systems had been used.
“The precast panel solution affords a greater level of quality control with each panel being delivered at a level, which we’re confident surpasses anything that could typically and reasonably be achieved on site,” Mr Townsend says.