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Thursday24 July 2014

STEEL FOCUS

The St Alphege building, University of Winchester by Design Engine

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Design Engine’s new teaching block for the University of Winchester is dominated by a steel-and-timber portico inspired by Christian symbols

With its 12m-high steel portico and distinctive Christian-inspired artwork, there’s no missing the University of Winchester’s new Learning and Teaching Building.

Designed by local practice Design Engine, the St Alphege building is the latest facility to be added to the former King Alfred teaching college’s campus, following its reincarnation as first University College Winchester in 2004 and then the University of Winchester in 2005.

Design Engine has worked extensively on the campus, which occupies a steeply sloping site on the outskirts of the city. The St Alphege building, which was officially opened in January, helps to form a new public space bounded by the University Centre — completed by the practice in 2007 — and the theatre, which the practice refurbished in 2003.

University of Winchester teaching block by Design Engine

University of Winchester teaching block by Design Engine

Faced with an urgent need for improved and additional teaching space, the university decided to redevelop an inadequate 1920s arts block in front of the library to provide eight flexible teaching rooms for up to 600 students.
Design Engine’s eventual solution also creates a linking block to the adjacent 1970s St Edburga building, which has been reclad and given a lightweight, steel-framed rooftop extension containing two further teaching studios.

As well as providing the accommodation the university required, the architects were keen for the building to create a suitably impressive presence on the new piazza, which has become an important outside social space on the campus.

“My worry was that a teaching building wouldn’t have a frontage with some element of closure to what would be an important public space,” says Design Engine director Richard Jobson. “So we developed the idea of a large oversailing roof with an opportunity for an artwork.” The grandiose steel atrium also facilitates pedestrian flow through to the green space alongside, known as the Dytch, Jobson adds.

Another important factor was the nature of the adjacent St Edburga building, which has floor-to-ceiling heights of just 2.3m. Ideally, the architects would have wanted to provide level floor plates to ease the transition between the two buildings, but this was problematic because of the desire to provide higher teaching spaces in the new accommodation. The practice therefore opted to make the ground floor of teaching studios double height (4.5m) so that the first floor could align with the new upper storey of St Edburga.

University of Winchester teaching block by Design Engine

Source: Heyne Tillet Steel

Structural steel model

Steel was the only viable option for the primary structure, according to engineer Heyne Tillett Steel, because of the intense time pressure to complete the St Alphege building before the 2012 autumn term (the St Edburga phase completed early this year). As a result, the programme was accelerated, with the design detailed and procured at speed in order to finish in time. In total, steelwork contractor Snashall Steel Fabrications Co supplied 300 tonnes of steel.

The building is constructed with a steel superstructure with composite beams, highly insulated rainscreen cladding and blockwork walls. The 12m-span precast concrete planks provide thermal mass and use integral water pipes as part of an active cooling and heating strategy.

On the south side of the building, the recessed elevation is overhung by a 1.5m-wide colonnade of large brise-soleil blades. The colonnade’s eight steel columns are syncopated with alternate wide and narrow gaps; these are balanced with a pattern of timber slats that the architects derived from an overlapping “golden rectangle” proportioning system. Rather than running continuously, says Jobson, the pattern is broken so that students don’t feel as if they are imprisoned inside. “It’s a repetitive pattern that you break with an alternative pattern that also repeats. It has a rigour but also a certain account of freedom,” he adds.

The glazed link between the St Alphege and St Edburga buildings contains the main entrance and is dominated by a purple “scissor” steel staircase which leads to teaching floors, as well as a mezzanine with computer and desk space.

University of Winchester teaching block by Design Engine

Source: Nick Kane

Two layers of larch brise-soleil help to animate the side elevation

The staircase is cantilevered 5m from the edge beams on each landing, with hollow section stringers further stiffened by a welded steel plate balustrade. This solution avoids the intrusion of support structure into the circulation space. Instead, each half landing is supported only by the staircases going up and down from it. The curved staircase has a randomised pattern of circles cut into the plate balustrade.

But it’s the portico that steals the show. This provides a frame for the artwork, designed by the architects in consultation with vice-chancellor Professor Joy Carter. She wanted a piece that would reinforce the relationship of the university with its Christian heritage.

The work represents Christ surrounded by the apostles, denoted by suspended steel boxes, with the exception of a rusting weathering steel element that represents Judas. These are linked by 30 polished rods in reference to the 30 pieces of silver that was the price of Judas’ betrayal. Two Douglas fir timbers form a cross. Other elements include thin vertical strips of larch, which symbolise the population of the college.

The architects have made the most of views through the building, with a full-height window opening onto the portico from the lower teaching level, and visual connections through the linking building to a new rear courtyard.
The new building is designed to achieve a Breeam rating of “Excellent”. The entire project, including the adjacent building’s steel-framed upper floor, cost a total of just £3.8 million at a rate of £2,150 per sq m. “There’s a lot of building, and a lot of complexity,” says Jobson.

Portico

A 12m-high galvanised-steel frame creates a suitably impressive portico. Steelwork contractor Snashall Steel created two 850mm-wide and 200mm-thick corner fins using steel “ladders” clad in powder-coated aluminium panels. These are of different heights to accommodate the sloping site.

“The architect wanted to see fins, so we used a double column arrangement to support the weight of the artwork structure,” says Heyne Tillett Steel project engineer Andrew Blasdale. “The ladder arrangement gives fixing positions to the cladding and provides nominal interconnecting restraint to the two columns in their weaker direction.”

The frame contains an oculus — originally intended to be positioned above a reflecting pool — which throws a circle of light onto the ground and backlights the artwork.

Due to the cost and programme constraints on the project, Snashall Steel decided to use four corner beams at 45 degrees to provide an octagon. This was then finished off with plywood to create the curve.

Rooftop extension

University of Winchester teaching block by Design Engine

One of the trickiest aspects of the project was creating the lightweight steel-framed storey on top of the St Edburga building. Although the skeleton portal frame was fairly standard, the challenge was getting the setting out rightBecause the base building wasn’t quite square, according to Snashall Steel technical director Blair Thomas. “The whole thing sat on top of the existing structure and fixed into the masonry,” he says, adding that this was achieved using chemical anchors.

The existing roof finishes and toppings were removed and the original brick piers were tied into the new steel columns.

PROJECT TEAM
Client
University of Winchester
Architect Design Engine
Main contractor Geoffrey Osborne
Structural engineer Heyne Tillett Steel
Steelwork contractor Snashall Steel Fabrications Co

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