Directional mass dampers for buildings under wind or seismic loads

Three passive damper configurations are studied for buildings: unidirectional dampers oriented to the story principal axes and dampers with a single mass attached to spring-dashpot elements laid out at 90°/120° to each other. A simple damper design procedure to minimize a weighted combination of RMS building responses, using the concept of structure-constrained feedback control, is presented. Examples of six tall buildings with roof dampers and various plan geometries are considered. Performance of the simple dampers under along/across wind loads and seismic excitation are studied. With varying loading direction, unidirectional dampers show differing levels of control performance; however, performance of the latter types of dampers appears independent of excitation direction. For multi-winged buildings a good damper seems to be a single mass connected to one set of spring-dashpot elements for each wing; for wings exactly or nearly aligned with each other, a single spring-dashpot unit in one of them appears sufficient. Numerical results for performance and effectiveness of the dampers are presented and discussed.