To the Geordie passerby, the large timber lattice roof, now emerging above the hoardings of a central Newcastle site, appears little more than a web of wooden beams supported on steel columns. But tell him he is looking at a 'global garden' of growing structural trees cocooned beneath a 'living' timber framework which was conceptually inspired by the shape of a leaf, and, 'appen as not, he will smile politely.
To really capture his attention though, he should be told that this 1.5M framework is one of the most complex geometrical roof shapes yet created in steel and timber. It contains no straight lines and its 1,500 pieces make up a jigsaw that took engineers four times as long to design compared to a conventional structure because its profile defied every mathematical principle they had been taught.
'It has been one of our company's biggest challenges so far,' recalls Paul Bates, associate with consultant Mott MacDonald. 'The roof has no analytical or mathematical shape so we had to develop a way of turning an architect's sketch into something we could analyse and impose loads on.'
The structure that has dominated Bates' professional thoughts for the last couple of years is to become the visitor zone for the International Centre for Life. As its name implies, this is yet another of those pioneering schemes designed to capture both a new way of entertaining and educating the public and also securing a sizeable grant from the Millennium lottery fund - roughly half the 55M overall cost.
As one of the Millennium Commission's 14 landmark projects, the centre claims to be a world first in concentrating on one site a range of activities based on the genetics and understanding of life itself. Client, the Centre for Life Trust, will host research, education, commercial outlets and public entertainment, all geared towards providing a better appreciation and use of life's core structure - DNA.
Already, a 12M Bioscience Centre is structurally complete and being fitted out to house commercial laboratories and companies keen to develop the fast growing biotechnology market of pharmaceuticals, medical testing and X- ray equipment.
Alongside is the near complete Genetics Institute, a similar four storey concrete frame building earmarked as a new home for Newcastle University's genetics research team. And by this time next year, some 150 scientists and academics should be investigating the causes of numerous life-threatening inherited and infectious diseases.
But the site's challenge for civil engineers is already visible. Adjoining the Institute will be arguably Britain's most high-tech visitor centre.
Here up to 280,000 visitors a year will be gently coaxed into understanding life's basic building blocks through a 10M package of futuristic interactive displays. And to house this genetic theme park, architect Terry Farrell & Partners specified a building that was itself to be themed on life.
But for its structural consultant, the vast 75m long Global Garden started life more humbly - as a block of polystyrene. 'We gradually shaped it using a Stanley knife, shaving off bits like a loaf of bread,' Bates recalls. 'The whole design is driven strongly by the architect and we needed some form of model from which to start to get onto his wavelength.'
Mott MacDonald's brief was essentially to look at nature; to analyse its efficiency in structural form - hence the leaf study - and to then design a structure sympathetic to these 'life forming' principles.
'We spent a lot of time drawing veins on leaves,' recalls Bates with a wry smile. 'The problem was a structure doesn't just evolve and grow like nature, it has to be put together fully formed.'
And there was a second equally pressing problem. The chosen shape - the 'realisation of an architectural sculpture' in Bates' words - was a genuine freeform structure impossible to analyse analytically.
In hindsight, the consultant's solution appears totally logical. Standard AutoCad programs were used to convert the architect's sketches into a grid of nodes. Mott MacDonald then developed its own in-house software to transform this 3D Cad shape into an analytical model on which loads and moments could be imposed and tested.
'The model simulates curved members using short straight lines,' Bates explains. 'To achieve an adequate simulation of this curved geometry we needed 796 node points and 1,678 joining members.'
The result, now 80% complete, is much easier to understand. Built by Westbury Tubular Structures, subcontracted to main contractor John Laing, the frame is basically 10, up to 45m long, two-pin curved portal frames arches, each formed of four laminated Glulam timber beams.
Using timber offered engineers flexibility to achieve the desired awkward shapes. And adopting such phrases as 'a living material' also scored brownie points with the architect.
The inclined columns supporting each portal arch are simply 400mm diameter tubular steel members. But raking them in groups of three from a common base, and calling them structural trees, gains loads more architectural points.
The roof could quite practically have been designed as self supporting. But, by clustering the columns in raked groups, they take little floor space. And, with the entire internal structure being left exposed to public gaze, there are sufficient columns to - in architectural speak - 'make their own statement'.
Accompanying this one-off design have been the not unfamiliar construction challenges of learning curves and design development holdups. The result is a roughly six week delay on roof erection.
But the site team remains confident that the framework will still be up and clad in copper by next Easter as scheduled. This allows a full year for the cutting edge 10M Disney style fitout before the visitors arrive in spring 2000.
Paul Bates is optimistic that, despite the interactive attractions and themed rides, at least some of the tourists will glance upward at his trees and timber lattice. 'It has been a valuable experience, but now I long for a structure with just a few straight lines in it,' he concludes.