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Partial safety factors (y-factors) first appeared as a coherent system for dealing with the uncertainties involved in structural design 30 years ago. For nearly a quarter of a century they have been a feature of at least some design Codes in the UK. They are now used for most main UK design Codes and many European Codes and are the approach adopted for the Eurocodes.
Professor A.W. Beeby
Though some engineers object, most modern structural Codes or design standards use partial safety factors, i.e. y-factors. With certain exceptions, there are generally two y-factors - yf for loads and ym for resistances.
Popper has argued that the growth of scientific knowledge takes place as a result of the falsification of theories. Some of his ideas can be applied to engineering knowledge as well, but the falsification of the calculation procedure model (CPM) cannot actively sought. When engineering failures do occur, therefore, they provide invaluable opportunities for the growth of engineering knowledge, provided that we can isolate the component of the CPM that has been falsified. The two cases of failure discussed in this paper indicate that the design philosophy component of the CPM has been falsified. The two resulting suggestions for changing the CPM are (i) to control the progression of collapse in a structure so that greater warning given and (ii) to take into account the sensitivity to deviations from specifications when selecting structural alternatives.