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Newton Park Campus Bath Spa University Reference: www.cnplus.co.uk
A Major construction project built in grounds involving complex logistics.
When renowned Georgian garden designer and landscape architect Lancelot 'Capability' Brown rejigged the land around Newton Park Country House in north-east Somerset, he probably wasn't thinking that 250 years later the sloping lawns, terraced lakes and meandering driveway would be enjoyed by students relaxing after their exams. The beautiful parkland setting that this Bath Spa University campus enjoys is proving a bit more of a headache to Skanska operations manager John Brennan and construction manager Simon Dawson. "The land is all leased from the Duchy of Cornwall and we have to work under a Natural England Licence," says Mr Brennan. "They approve all our work and one of the fundamental points is that the land has to be returned back to the original capability Brown contours. It's very tightly controlled."
With the hundreds of tree preservation orders around the site, existing teaching blocks, student accommodation and difficult access, what most would assume is a spacious greenfield site is actually as logistically challenging as any city centre project working around the term-time requirements of the students, the team began its 10-week enabling works contract in March 2012.
With pipistrelle bats thought to be resident in the 1960s-built student accommodation blocks, the teams worked under a bat licence before starting the hand strip of the roof tiles and demolition of the old halls of residence. Once sie workers had removed the topsoil, the basement dig could get underway for the BREEAM Excellent-targeted twin winged teaching block and media centre.
"The topsoil has been put aside and will be reused," says Mr Dawson, "and we hit the fractured limestone bed rock at barely half a metre below the surface."
With formation level of the basement to the two wings sitting at 8m deep,there has been a lot of limestone to dig out, but all of it has been crushed and recycled as backfill and used to repair car parks around the parkland. One benefit of that underlying limestone is that the pad foundations for the building are cast directly onto it. The basement itself features a 450mm-thick reinforce concrete slab with 300mm-wide walls bringing the the building up to ground floor level. From there and up to it's second floor roof level, a structural framing system takes over with the aid of a concrete frame.
This is based on a nominal 7.6 m grid with 450 mm diameter columns and 500 mm by 300 mm perimeter columns. "There is not a great deal of vertical concrete," says Mr Brennan."Just minima l columns really."
Cast in situ slabs feature exposed soffits with 2.4 m wide,900 mm deep transfer beams enabling the team to open up the spans to provide the flexible lecture space it wants for the students.
The biggest concrete pour for the slabs was carried out for the roof of Block B,with 240 cu m carried out in a single day. Forty concrete delivery wagons feeding mobile pumps throughout the day proved a test for the project's delivery management system, but the team battled through. "We had a tower crane there from August principally to help us through the superstrncturework," says Mr Dawson. Throughout the main section of the buildings there are four stair cores which move up an average of two-and-a-half flights. Each of these flights have been precast on site by concrete frame manufacturer MPB Structures.
Conventional wisdom would suggest that the advantages of prefabricating the stair sections are that they are produced in factory conditions enabling perfect casting.Precast production on site, and all those advantages of being able to dictate perfect casting conditions fly out of the window. But for the team at Bath Spa it made perfect sense. With the size and length of the stair flights varying there was no opportunity for precasters to gain the repetition they need to make their work profitable. They were quoting some sky-high figures and the team realised that the advantages were there for the frame contractor. With it's presence on site anyway, MPB just neede to divert some of it's attention to fixing stair formwork and casting.
"MPB had it's lads in as an overhead anyway so it made sense for them to do it. It also meant that the sequencing was down to them. They were the masters of their own destiny," says Mr Dawson.