As the name implies, the Manchester Aquatics Centre is not your average leisure complex: as well as offering flume rides and a toddlers' paddling pool it also caters for every aspect of competitive aquatics, including solo diving, synchronised diving, synchronised swimming and water polo.
Commissioned by Manchester City Council in collaboration with the three universities in the city, it can be used by students and locals. However, the complex will also be one of the major venues of the Commonwealth Games which are to be held in Manchester in 2002.
The new pool building fronts the busy Oxford Road and forms part of the UMIST campus; student halls of residence are behind and the building is adjacent to the new school of management, designed by ORMS.The gable end on the west faces the main road; the 100m long south side - a series of stone-clad service 'chimneys' and glazed walls - forms one side of a new pedestrian public space and contains the main entrance. Visitors enter a wide double-height reception which leads to the cafe and pool hall, a 'heroic' 32 x 100m space.
The central pool, the 50 metre competition pool, has underwater observation windows and a constant 2m depth which can be made shallower by two movable floors; the pool can also be divided by submersible booms. At the east end, a 5 metredeep diving pool incorporates underwater observation windows and a retractable floor. The cast in-situ concrete diving platforms have 3m springboards together with 3, 5, 7 and 10m fixed platforms.
At the west end of the hall is a free-form shallow-water lagoon for children; a play area, flume rides and bubble pools are landscaped with artificial palm trees, emphasising the leisure, as opposed to serious swimming, function.
Supporting accommodation is arranged in a three-storey concrete-framed structure along the south side of the pool hall.The changing village and the health suite are set on each side of the doubleheight reception, with a cafe overlooking the pool.
Upper levels contain a fitness suite and a dance studio, and give access to the main spectator gallery of 1,000 seats which will be used for the Commonwealth Games. For such occasions extra temporary seating can be provided, in part, over the leisure area to give up to 2,500 spectator spaces.
The mechanical and water-treatment plant is contained in the basement. This also contains a unique facility, an additional 50m training pool whose purpose is to provide dedicated elite swimming training. The pool has a traversible boom to adjust its length to 25m, and a retractable floor to allow water of varying depth for teaching; it has its own storage and changing rooms, a sports-science room, a sports-medicine room and a land-training room containing isokinetic fitness equipment.
The structure The 32 x 100m pool hall is a column-free space formed by a steel roof structure which arches asymmetrically over the pools, reaching almost 20m at its apex and spanning 37m over the spectator seating. Along the north elevation and facing the spectator seating and entrance runs a series of plate girders 7.7m apart, which spring from stoneclad thrust blocks. They rise, increasing in depth and curving to meet a flattened ridge, a double ridge truss flanked by rooflights; at this point the plate webs change to trusses which slope down to the south elevation to bear on cast-in-situ concrete columns and core walls beyond. They are partly screened by a waved acoustic ceiling which helps to provide the acoustic environment needed for the voice-alarm evacuation system.
Eight of the plate girders are deeper than the others and are arranged in four pairs, with horizontal and diagonal CHS purlins and bracing members between them. The pairs are located at the gables and at mid-point, at each side of the main staircase. The gable girder pairs are braced with additional CHS props which are pinned from the bottom boom of the outer girder to the top boom of the inner girder to stabilise the gable and transfer wind loads from the gable to the roof plane. These pairs of frames support the ridge trusses, which in turn support shallower intermediate frames.
The top and bottom flanges of the main girders are made up from 254 x 254mm universal columns with 12mm thick steel plate webs welded between them. A 20mm thick, 254mm wide steel plate replaces the universal column for the top flanges of the intermediate frames.The girders are set at 7.7m centres and are braced by a series of horizontal CHS purlins welded to the webs, providing lateral stiffness and creating a simple and elegant structural rhythm along the north wall. The webs of the girders were welded in sections; the welded junctions are designed to occur where the CHS purlins are welded to the webs. The junction is concealed by stiffener plates which, together with the site-welded purlins, give lateral stability to the structure.
The difference between the paired girders, acting as box trusses, and the smaller girders which run between them is emphasised by a subtle change in soffit treatment. The smaller girders are lined with a perforated acoustic structural 'Kaltray'; the large paired girders are lined with structural 'Kal-deck', a more articulated trapezoidal profiled liner.
The west gable of the pool flanks the pavement and busy highway of Oxford Road. The strongly curved girder form is reflected in the verge which is clad with silver-coated Luxalon sheet, cut and flashed to replicate the girder shape behind it. The curtain-walling system below it comprises a polyester powder-coated aluminium frame with bands of double-glazed units of clear glass inset with adjustable micro-blinds, and opaque ceramicbacked glazing units backed with insulated aluminium trays.The facade is divided into horizontal bands by painted steel walkways with GRP grid floors; they give solar shading, articulate the facade and give access to the curtain wall for maintenance.
Protecting the steel structure Steel was the natural choice of structure for the pool, for its ability to span large volumes economically. The technology of corrosion prevention has been highly developed for areas with much greater risk, such as oil exploration platforms. The fabricated steel components were shot-blasted and treated with 50 micron epoxy zinc-phosphate primer, a barrier coat of 125 micron micaceous iron oxide followed by a 50 micron decorative top coat.
Steel mullions supporting a glazed gable wall As the roof structure runs for 100 metres without movement joints, it was necessary to design the gable wall as an element of structure that allowed the roof to move above it.
The gable wall structure consists of a series of fabricated steel mullions at 3.6m centres. They support the gable wall and the walkways with a top fixing that accommodates movement of the roof structure in three planes.
In section each mullion is an asymmetric oval, tapering at one end. It is formed of an inner 406 x 178mm UB lined with 12mm steel plate. The curved ends are formed by CHS tubes cut in half; a half-tube of 244mm diameter is welded to one flange; the other flange is shortened and welded to a half-tube of 114mm diameter.
Each mullion has a welded lug at the top which slots inside a pair of plates welded to the bottom flange of the outer gable girder. The slot allows the girder to move up to 1015mm vertically and horizontally.
An insulated sliding movement joint is incorporated in the cladding on the same plane.
The gable mullions are restrained by a series of CHS props which retain the mullions within the slots. The lower props are horizontal; the topmost prop is curved to follow the line of the girder.
The walkways are supported on brackets that cantilever from the main mullions and are additionally propped by 25mm diameter rods suspended from the verge. The rods are held by tapered T-sections connected to the bottom boom of the gable frame.
A 50mm structural thermal break penetrates the facade at all connections.
ARCHITECT FaulknerBrowns: Nick Deeming, Jean Paul Colback
STRUCTURAL ENGINEER Ove Arup & Partners, Newcastle on Tyne: Gordon Mungall, Sarah Clemmetsen, John Gregory
MECHANICAL & ELECTRICAL ENGINEER Ove Arup & Partners, Manchester
WATER TREATMENT ENGINEERING FaulknerBrowns Engineering Services
QUANTITY SURVEYOR Tozer Capita
MAIN CONTRACTOR John Laing Construction