New assessment methods for the residual safety of old steel bridges

A great part of existing steel bridges for roads and rails are riveted structures that were built in the last century. Many of these old bridges have undergone several phases of repair or strengthening after damages in the world wars or due to changes of service requirements. For these bridges the question of the actual safety for modern traffic loads and the remaining service life is put forward. This paper describes a procedure to determine the residual safety and service life of old steel bridges and how a basis can be established on which economic decisions for further strengthening or replacement by a new bridge may be made. This procedure has been developed in close cooperation between the Institute for Ferrous Metallurgy and the Institute for Steel Construction of RWTH since 1982. It has been applied to many steel bridges in particular in Eastern Germany and also to other structures susceptible to fatigue, e.g. guyed masts, antennae, machinery parts etc.