String structure defies nature

30th June 2006 at 01:00
An engineering competition in Bristol challenges students to design earthquake-proof structures. Andrew Mourant watches Year 9 students deal with the ups and downs

In just a few seconds, an earthquake can make rubble of buildings that took years to design and construct. Along fault lines from Turkey to Taiwan, engineers and architects strive to find ways of withstanding destructive shudders that emanate from the Earth's crust.

Groups of Year 9 pupils from several schools in Bristol have also been doing this. Each year, they compete in a challenge set by the university's civil engineering department to build structures that can withstand an earthquake simulator.

Part of the IDEERS project (introducing and demonstrating earthquake engineering research in schools), the competition is a test of ingenuity, in which they use strips of wood, glue, string and paper.

There are strict rules: minimum height; at least three floors; minimum distance between storeys; space to be left for windows; and proportionate floor space on each level strong enough to bear steel blocks weighing 635 grammes.

The design requires planning and thought. And the outcome can be surprising: one winner this year was an unlikely edifice held together with bits of string, standing - just - long after more elegant structures bit the dust.

The competition, involving 14 schools over two days, has resulted from a partnership of Bristol University, the LEA and the science exploration centre, At Bristol. Undergraduate engineering students help on the day if needed and advice is obtainable in advance via a website.

"We want children to find things out on their own," says Dr Wendy Daniell, research fellow in earthquake engineering. "Teachers aren't meant to do hands on."

The event is targeted at top-ability Year 9 groups in city comprehensives where the idea of doing engineering at university may seem a remote possibility. One school, Speedwell, has incorporated it into the structures element of its work scheme for Year 9 and developed a booklet to go with it.

"In class, we put up on the board examples that survived the simulator almost until the end, yet students don't come up with the same examples year after year," says Rob Boyd, curriculum leader for DT and ITC.

"They say, 'No, we wouldn't do it that way - we'd do it another way'. The project works with all abilities."

Wendy says that past competitors have been inspired to go on and do maths and physics at A-level. "We want them to recognise their own potential and think about going to university," she says. Some competitors are more prepared than others.

"We did about 10 models beforehand," says David Penrose, a science teacher at St Mary Redcliffe and Temple School. "But I've had no input whatsoever - all I've done is supervise."

The St Mary model is first to take shape and be completed. It looks a confident piece of work. But others are struggling. Tom, Gary, George and Sam, from Bedminster Down, begin by trying a pyramid structure but abandon it after 50 minutes and have to start again.

Despite their race against time, original ideas take shape, such as arches to spread the load; though between battling the clock and the glue gun, these are not always well executed.

"Aesthetically I'm not very pleased with it," says Tom, Bedminster's team leader, as time ebbs away. At another table, Hengrove Community Arts College team has fashioned a fortified pyramid shape that looks robust enough to withstand any shake high up the Richter scale.

But the last building left standing doesn't necessarily win, as Dr Adam Crewe, lecturer in earthquake engineering at Bristol University, explains.

"We want them to go for strength but also lightness of weight - that's what real engineers are encouraged to do," he says. "It's quite difficult to get the balance."

Failure can come about if the structure rocks too much or more than half the columns give way, if a floor collapses or any of the steel blocks that represent people fall out or move too much - or if there's any other failure "that would cause death to those inside".

Time's up after four and half hours. There's a late scramble for some but all have completed a model to take up for testing on the university's earthquake simulator. There are no fallers at the first or second shake, which meant, in theory, that all the structures would withstand any tremor that occurred in Britain during the past 100 years.

But then, with the intensity turned up, they start going down like falling horses in the Grand National. In the end, Hengrove's pyramid and Bedminster Down's ad hoc creation stand firm, despite being shaken by a force equal to the strongest earthquake ever recorded.

But they have shed weights - in Bedminster's case early on - which rules them out as winners.

First prize goes to the string-clad structure built by an all-girl team from Monks Park. "That's what we should done," says Tom ruefully. "Built it weedy but used lots of string."

* www.ideers.bris.ac.uk

* www.bristol.ac.ukcivilengineeringresearchstructureseerc

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