Bridge Design: Reality Bites Back

Many bridge engineers tend to ignore the process nature of reality, the fact that everything in this universe changes from moment to moment. When they are given the responsibility for rehabilitating an older bridge, they often ignore changes that have taken place. Examples, taken from a decade of review of proposed redesigns Ohio bridges, include a railing too detached from its deteriorated concrete slab to restrain traffic scheduled next to it, failure to note the difference between rain and actual bridge drainage, and failure to check for settlements that may have taken place over several years. Other designers, seemingly unaware of research into metal fatigue, ignore the fact that fatigue cracks generally show up at the point of 85% useful life of the member and that where one member is cracked, its neighbors soon will be. Observant engineers, however, will have trained themselves to be acutely aware of changes and therefore able to evaluate their significance and respond appropriately.