ALL structural engineers are familiar with the simple structure that is in fact difficult to design in precise terms because of uncertainties in the assumptions on which any accurate analysis of stresses can be based. The road is a notable example of this because the analysis of stresses in a slab supported on a foundation that is at best only semi-elastic is not an easy matter and, in addition, because stresses due to
temperature changes are almost as important as those due to the applied loading. Another factor is that structural failure in roads is seldom a definite phenomenon. It takes place over a considerable period of time and can often be counteracted by increased maintenance work or resurfacing. Therefore, there is not the same need as in other structures to allow for a substantial “factor of safety,” the design being a compromise between first cost and length of life. For a stress analysis to be of much value in these circumstances it must achieve a considerable degree of accuracy.
A. R. Collins