In 1953. the author of this note suggested that approximate calculations for the behaviour of a suspension bridge under superimposed loads might be based upon a foundation analogy in which the cable was replaced by an elastic foundation of modulus k = a . w/d, . . . . . (1)
where w is the dead weight of the bridge per unit length (treated as uniform) and d is the dip of the cable. The stiffening girder of the real bridge is then treated as a beam on an elastic foundation with this modulus. The coefficient a, in this expression, by consideration of the resistance of a heavy inextensible * cable to
displacement by vertical loads, was shown to be of the order of 20, but it was pointed out that in practice the choice of a must, in the limit, be empirical.
Sir Alfred Pugsley