Nonlinear Dynamics and Control of Moving Slender Continua Subject to Periodic Excitations

Tall structures often sway with large amplitude and low frequency due to resonance con-ditions induced by wind loads and long-period seismic excitations. These sources of exci-tation affect the performance of vertical transportation systems (VTS) deployed in these structures. The fundamental natural frequencies of tall buildings fall within the frequency range of the wind and seismic excitations and the sway motions form the excitation mech-anism which acts upon the VTS. Particularly affected are long moving slender structural components such as the suspension ropes, compensating cables and travelling cables. Complex nonlinear resonance interactions arise in the system when the frequency of the excitation is tuned to the natural frequencies of those elements. The methods to mitigate the effects of dynamic interactions in a high-rise VTS involve the application of passive and active control devices attached at the compensation sheave assembly. In this paper a numerical simulation model is presented to predict and analyse the resonance behaviour of the system equipped with a nonlinear damper-actuator system. The performance and characteristics of this device can then be optimized and adjusted to minimize the effects of adverse dynamic responses of the system.