Resonant Vibration of Steel Stacks

Soon after their completion, the steel stacks of the Moss Landing steam plant (south of San Francisco, Calif.,) were excited to violent vibrational movement by a steady wind of moderate velocity. These stacks were conservatively designed in accordance with commonly accepted practice and were capable of withstanding, as a static force, the drag from a wind of several times the velocity which occurred. Investigation indicated that vibration was caused by periodic forces which developed during the formation of von Karman vortices in the air stream around the stacks. There are cited herein the character and magnitude of the disturbing aerodynamic forces, the investigation and studies made, and the design of corrective measures taken to protect the stacks from similar disturbances in the future.