The scope of this paper is to investigate the possibility of defining simplified non-linear dynamic systems that are capable of capturing and reproducing the fundamental natural frequency coalescing phenomenon, which has been observed under certain conditions, in the wind induced response of tall buildings. To this end, a system with two degrees of freedom, representing the two coalescent modes of the building, is considered, while the amplitude-dependent and therefore non-linear damping is investigated as a possible cause of the observed phenomenon. For this system the analytical time-invariant conditions under which the frequency coalescence can occur are firstly identified. Then, stationary exciting functions derived from experimental wind tunnel tests are considered, allowing the direct observation of the phenomenon by means of time-frequency wavelet analysis.
Analysis and modeling of natural frequency coalescing in the dynamic response of tall buildings
SPENCE, SEYMOUR MILTON JOHN;BERNARDINI, ENRICA;GIOFFRE', Massimiliano;
2012
Abstract
The scope of this paper is to investigate the possibility of defining simplified non-linear dynamic systems that are capable of capturing and reproducing the fundamental natural frequency coalescing phenomenon, which has been observed under certain conditions, in the wind induced response of tall buildings. To this end, a system with two degrees of freedom, representing the two coalescent modes of the building, is considered, while the amplitude-dependent and therefore non-linear damping is investigated as a possible cause of the observed phenomenon. For this system the analytical time-invariant conditions under which the frequency coalescence can occur are firstly identified. Then, stationary exciting functions derived from experimental wind tunnel tests are considered, allowing the direct observation of the phenomenon by means of time-frequency wavelet analysis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
