Page 23

0603NSCMarch06

Commercial At the Willis Building Construction Management has been combined with close cooperation between the key trade contractors, who were brought on board at a very early stage. For the main superstructure, Mace got the main players together as soon as it was appointed. Stanhope Technical Director Peter Rogers asked for a comparison to be made between post tensioned concrete and steel, so concrete contractor La- ing O’Rourke, steel specialist William Hare and the scheme’s structural engineer whitbybird were brought in to compare the costs and engineering merits of the two. “Time wise, concrete was faster and not so crane de- pendent,” says Mr Moore. “Concrete was also initially cheaper, because you don’t have to fire protect it. But it was much, much heavier, which would have added too much cost and time onto the piling and substructure.” At the Willis Building Mr Moore had some reservations about lining and Construction leveling which were resolved by incorporating a jump- form concrete core. “The advantage of the core is Management has that we can fix into it with cast in place plates, which been combined with gives us a bit of flexibility,” explains William Hare Director Nick Day. “To us that’s the best solu- close co-operation tion.” between the key trade A prefabricated decking solution was selected – something that had been used contractors before but not on the scale of the Willis Building with its complicated floor plates. Using prefabricated decking, with large sheets designed to fit exactly, means there is no on site cutting. The result is a quieter, faster decking process. According to Mr Day, decking contractor Richard Lees Steel Decking was initially unsure if the prefabrication would work on a building of this complexity, but it proved to be the right decision. Richard Lees Steel Decking Managing Director Nick Grimsey said: “We faced Using prefabricated the logistical challenge decking with large of getting the correct pre- fabricated deck bundles to sheets cut to fit the right location on site, at exactly means the right time. By working there is no on-site facturers Corus Construction-closely with our deck manu cutting and Engineering Products, we established an efficient and ef- fective logistical process to overcome this.’ Fire protection also receives an innovative solution. Both the tower and the lower building are entirely glass-clad, with the façade columns exposed. Here, Foster’s design was for circular columns but, rather than going for an intumescent paint finish, whitbybird and William Hare developed what they call the “Lancashire Column”. This is a standard column section with plates welded between the webs and then placed inside a larger circular hollow section with the void filled with concrete. William Hare fabricated these structural columns and delivered them in two storey height lengths to site. Mr Moore is delighted that they don’t have to be fire protected at a later stage. “That’s one trade on site that I don’t have to worry about,” he says. “One trade whose materials I don’t have to lift up with each floor - which is great on high rise.” Since being appointed in June last year, William Hare and whitby- bird have worked extremely closely, with William Hare designers tak- ing up residence in the engineer’s offices to build a “virtual model” of the steel frame using Tekla Structures. “We built some of the models and they built some, and we passed them back and forwards,” explains whitbybird associate director Peter Chipchase. “There was an element NSC March 2006 23


0603NSCMarch06
To see the actual publication please follow the link above