Directional mass dampers for buildings under wind or seismic loads

Three passive damper configurations are studied for buildings: unidirection al dampers oriented to the story principal axes and dampers with a single m ass attached to spring-dashpot elements laid out at 90 degrees/120 degrees to each other. A simple damper design procedure to minimize a weighted comb ination of RMS building responses, using the concept of structure-constrain ed feedback control, is presented. Examples of six tall buildings with roof dampers and various plan geometries are considered. Performance of the sim ple dampers under along/across wind loads and seismic excitation are studie d. With varying loading direction, unidirectional dampers show differing le vels of control performance; however, performance of the latter types of da mpers appears independent of excitation direction. For multi-winged buildin gs a good damper seems to be a single mass connected to one set of spring-d ashpot elements for each wing; for wings exactly or nearly aligned with eac h other, a single spring-dashpot unit in one of them appears sufficient. Nu merical results for performance and effectiveness of the dampers are presen ted and discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.