From Clive Semmens
Tony Budd is right to criticise the kind of thinking that says, “this high-rise block of flats is designed to withstand a wind speed unlikely to be exceeded more than once in 100 years, so since its design life is 60 years, we have got 40 years to spare” (18 October, p 20). But he is wrong to say that “the correct interpretation would be that there is a 1 per cent chance that the maximum wind speed will be exceeded in any given year, or a 60 per cent chance in the building’s lifetime”. That would include the odds of the building blowing down twice or more.
If the risk is 1 per cent in any given year, then the risk in the building’s lifetime is (1 – (99 per cent)60), which is just over 45 per cent. I too find that understanding of this kind of issue is rare, even among engineers. It’s nuclear engineers I worry about.
Ely, Cambridgeshire, UK
