STEEL TRUSS BRIDGE REHABILITATION TECHNIQUE USING SUPERIMPOSED STEEL ARCHES (THE APPLICATION TO A MONTANA RAILROAD DECK TRUSS BRIDGE) . DEVELOPMENTS IN STRUCTURAL ENGINEERING. PROCEEDINGS OF THE FORTH RAIL BRIDGE CENTENARY CONFERENCE, HERIOT-WATT UNIVERSITY, ENDINBURGH, SCOTLAND, AUGUST 21-23, 1990. VOLUMES 1 AND 2