Moving load

A load which travels across a bridge, e.g., a train of wagons or vehicles, as distinct from a "dead" load such as the weight of the structure itself. Some times we speak of "live" loads in the same way. It may be noted that when a fast train suddenly comes onto a bridge the stresses are instantaneously twice what they would be were the train to be slowly loaded onto it. Influence lines offer a ready mean of assessing the effects of moving loads.