Vibration Measurements of Steel Transit Structures

Vibrations induced into rail rapid transit structures may be radiated from the structure as airborne noise that disturbs the rider and the wayside community, or as ground-borne vibrations that propagate into the foundations of wayside structures setting walls, floors, and common household items into annoying vibration. This report describes the results of field measurements on existing steel elevated structures presented to aid civil engineers concerned with design, performance, repair, and evaluation of steel elevated transportation structures. These measurements showed that peak acceleration levels are generated in decreasing order of magnitude on the rail, on the top and bottom girder flanges, on the girder web, on cross-bracing, on the column, and at the footing base. In addition, peak acceleration levels of 70 g are little attentuated as they are transmitted from the rail through the structure, and peak acceleration levels significantly increase for increasing train speeds.