Over the last two winters over 4,000 agricultural buildings have collapsed under the weight of snow, costing the agricultural industry £millions of pounds, as well as killing and injuring countless animals. Fortunately, there has been no loss of human life - but there have been some very close shaves.
Although some of the buildings that collapsed were undoubtedly old, and structurally weak, a few of them were relatively new or even brand-new. They collapsed because they were poorly designed, says Geoff Simpson, managing director of S&A Fabrications, and the vice-chairman of RIDBA - the Rural and Industrial Design and Buildings Association. These buildings were not as strong as they should have been, or easily could have been if better design principles had been applied to them.
The objective of the agricultural buildings industry now is to improve the strength of buildings to reduce the likelihood of buildings collapsing in the future, he told a seminar at the Agricultural Building Show, Stoneleigh.
“Farm building construction is unregulated in England and Wales,” he said. “In Scotland planners require evidence of structural design before they give the go-ahead for buildings, but that is not the case here. All we have is BS 5502 which covers the design of agriculture buildings, but complying with 5502 is not mandatory. It is more of a code of practice than a regulation.”
Buildings failed for a number of reasons over the two winters, he explained. These included:
- insubstantial foundations, or improper connections to the foundations;
- lighter steel structures being used than should have been used;
- a lack of strengtheners in the building and steelwork;
- bolt failure or insufficient bolts used;
- building spans being too wide;
- buildings being too near each other, with the effect that the snow fell off one building and through another.
He explained that adding supports throughout the building, such as compression stiffeners, lateral restraints on the flanges, torsion restraints, and other subtle steelwork supports would considerably strengthen a building for very modest cost. “These supports will only add a small amount to the cost of a building, but will strengthen it enormously. To illustrate good and bad practice he and the RIDBA have produced a DVD which looks at a case study of a brand-new collapsed building, and details the structural weaknesses that led to its downfall. The DVD also illustrates how the supports and tensioners could have made a difference.
His advice to farmers thinking about erecting a building is:
- to get three quotes, but not to assume they're the same;
- to consider getting engineer’s calculations for the building;
- to visit the manufacturer's premises and other buildings;
- to take references from other farmers;
- to insist on BS 5502;
- to insist on whoever supplies or erects the building is a RIDBA member.
“Different quotes may look the same but they can vary significantly in terms of what they are and how strong the building will be,” he says. “Ask what you are getting, and ensure that your potential supplier talks you through the quote so you understand it fully. Go and visit buildings and look for the supports and the tensioners. But remember, they don't have to be in every building, because building design differs for every building, and every location, as it takes into account height above sea level, topography, windspeed, and ground conditions. If the supports are not there then ask why they're not there, but bear in mind that the bigger the building the more such supports will be required.
“Finally, using a company that complies with 5502 or who is a RIDBA member will ensure that your building has been built to the latest recommended standards, and will take into account the views of the country's leading building designers and experts.
So far people have had some very narrow escapes with their buildings, he explained, with one dairy herdsman leaving the building seconds before his building collapsed, and another which came down while the farmer's daughter was riding her pony in it. Fortunately, she was at a gable end, rather than in the middle, and was unharmed.
“Please, don't leave your building design to chance,” concluded Mr Simpson.
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