Engineers building Scotland's biggest city centre shopping complex are as concerned about concerts featuring David Essex or the Bootleg Beatles as they are about construction problems.
For the tight building programme at Glasgow's pounds200M Buchanan Galleries is dominated not just by concrete deliveries but by performances at the adjoining concert hall plus activities on the roads and multi-level railways that invade the site on all sides.
'Night work must be geared around any concerts taking place; the adjacent underground demands vibration constraints and Railtrack's safety rules dominate everything we do beside and over the railways,' says Ray Eve, deputy project manager for management contractor Bovis Construction. 'But some of our major headaches occur on Saturday nights after pub closing time.'
The near structurally complete five floor concrete framed building, with its 56,000m2 floor space for 80 shops, now conceals many of the construction challenges.
The Glasgow to Edinburgh rail line passes unseen through its heart below an eight level multi storey carpark. And buses again flow along a city street squeezing beneath three floors hung below a bridge spanning the road.
Though a pain to its builder, the structure's central location should ensure financial success to joint developer Slough Estates and Henderson Investments. Positioned strategically at the junction of Glasgow's two major pedestrian thoroughfares, the complex is already near 100% let.
Glasgow claims to be the busiest shopping city outside London, and Buchanan Galleries will form the focus of a Millennium grant funded pounds10M 'Great Street' already being dubbed Scotland's Champs Elysee.
In the cut throat retail world, anchor clients are king and, though Bovis still has five months of work before the centre's March 1999 opening date, already half the building is cordoned off as a no go area for construction workers. Some 28,000m2 of prime shopping space was completed early and handed over to anchor customer John Lewis a year ago for its now ongoing pounds20M fit out.
Flexibility in layout, a large 9.6m column grid and floor slabs with integral beams to create maximum ceiling height, were this prestigious retailer's prime demands.
'And what John Lewis wants it gets,' states Eve, echoing his client's orders.
Lack of headroom for traffic was the main challenge where a city street passes through the site. This has resulted in a novel 'hanging' bridge from which three levels of shops and offices, that span the street, are supported. A combination of 5m deep lattice and plate girders, up to 55m long, now straddle the road at roof level with the floors hung beneath.
Even more difficult to construct, was the centre's second integral bridge - allowing the main rail route to Edinburgh to run under the building's linked multistorey carpark. Placing the bridge's seven, 200t braced pairs of plate girders over the railway could have been achieved in a single weekend track possession.
'But Railtrack wanted two years advance warning of the date,' Eve recalls. 'Instead we took nightly possessions and had to bring in one of the UK's largest mobile cranes for what turned out to be two expensive weeks.'
The use of over 400 minipiles, to support bridge beams either side avoided railway safety
problems with tall piling rigs. But not so for nearby tower cranes which soared up to 65m above the site.
Safety cutouts prevented any crane loads straying too close to the tracks, but Railtrack's requests for guy ropes to be tied to crane masts, to safeguard against toppling, were successfully argued against by Bovis.
'They would have restricted crane performance and could have added to the risks if loads had snagged in the ropes,' reasons Eve. Instead structural safety factors for the cranes were increased by overdesigning all nine so that masts were 50% thicker than needed for the operating heights used.
One of the cranes' last functions was to position 4,000m2 of precast concrete external cladding. These brick or sandstone faced 10t panels were precast by Canadian subcontractor Artex in its own Toronto factory.
Surprisingly, no UK supplier could match the pounds4.9M Artex bid which even included the cost of shipping UK quarried sandstone facing out to Toronto and then returning it to Glasgow in completed panels.
And an equally surprising shortage of Scottish bricklayers also made it more economic to use extensive areas of 'prefabricated' brickwork on the panelling rather than building conventional brick walls on site.