Experiments to determine the effects of impact, vibratory action, and a long-continued change of load on wrought-iron girders

Abstract

The author observes that the experiments which were undertaken, nearly twenty years ago, to determine the strength and form of the Tubular Bridges which now span the Conway and Menai Straits, led to the adoption of certain forms of girder, such as the tubular, the plate, and the lattice girder, and other forms founded on the principle developed in the construction of these bridges. It was at first designed that the ultimate strength of these structures should be six times the heaviest load that could ever be laid upon them, after deducting half the weight of the tubes. This was considered a fair margin of strength ; but subsequent considerations, such as generally attend a new principle of construction with an untried material, showed the expediency of increasing i t ; and instead of the ultimate strength being six times, it was in some instances increased to eight times the weight of the greatest load.