A new passive rolling-pendulum vibration absorber using a non-axial-symmetrical guide to achieve bidirectional tuning

A new, passive, vibroprotective device of the rolling-pendulum tuned mass damper type is presented that, relying on a proper three-dimensional guiding surface, can simultaneously control the response of the supporting structure in two mutually orthogonal horizontal directions. Unlike existing examples of ball vibration absorbers, mounted on spherical recesses and effective for axial-symmetrical structures, the new device is bidirectionally tuneable, by virtue of the optimum shape of the rolling cavity, to both fundamental structural modes, even when the corresponding natural frequencies are different, in such a case recurring to an innovative non-axial-symmetrical rolling guide. Based on Appell's non-holonomic mechanics, a non-linear dynamic model is first derived for the bidirectional absorber mounted on a 1-storey 3-degrees-of-freedom linear structure translating under the effect of both imparted base motion and applied dynamic forces. A laboratory-scaled prototype of the device is then tested to experimentally demonstrate the bidirectional tuning capability and to validate the mathematical model. The design procedure and the seismic performance of the absorber are finally exemplified through numerical simulation.