The project comprises the Bioscience Centre which has a four-storey reinforced concrete frame supported on approximately 200 continuous flight auger piles, and the larger Institute of Human Genetics (IHG)/Visitor Attraction consisting of three inter-linked structures: the IHG, which has a four-storey reinforced concrete frame; the two-storey steel-framed black box; and the Global Garden.
The Global Garden was by far the most challenging structural element of this project.
The glulam framework with steelwork columns is, we believe, one of the most complicated geometrical roof shapes yet created in steel and timber: truly a free form, it contains no straight lines and is made up of a jigsaw of more than 1500 pieces. It is 75m long and 19m high at its tallest point. The main frame consists of ten, two-pin curved glulam arches. up to 45m long.
Since the Global Garden has no recognisable mathematical shape, Mott MacDonald had to develop a way of turning the architect's design sketch into something that could be fully analysed and on which it would be possible to impose loading. The form was first defined in polystyrene, shaped with a Stanley knife - like shaving bits off a loaf of bread.
Standard AutoCAD programmes were used to convert the sketches into a grid of nodes.
Mott MacDonald then developed its own in-house software to transform this 3DCAD shape into an analytical model on which loads and moment could be imposed and tested.
The model simulated curved members using short straight lines. To achieve an adequate simulation of this curved geometry there were 796 node points and 1678 joining members.
The inclined columns 'supporting' each portal arch are simply 400mm diameter tubular steel members. The roof could quite practically have been designed as self-supporting, but by clustering columns in raked groups, they take up little floor space and produce a treelike effect, further reflecting the natural fork of the roof.