Revision of the Niagara Railway Arch Bridge

The revision of the Niagara Railway Arch Bridge made in 1918-19, as here described, comprised first a complete investigation of live loads for railway bridges, in order to determine the probable maximum loading for such a terminal bridge–a double-track, two-hinged, 550-ft. arch over the Niagara Gorge. In 1918 an extensive series of strain-gauge readings, the methods of which are fully described, was made. The dead load stresses were investigated by jacking apart one top chord of the arch span by means of a special toggle, the center top chord dead load stress being read with the strain gauge. This resulted in the jacking open of both top chords in 1919 to change the center shims and readjust the stresses in all members of the arch trusses.