Vibration Mitigation without Dissipative Devices: First Large Scale Testing of a State Switched Inducer

Resonances of slender structures such as bridges, towers or cables are usually mitigated by dampers of various types or/and dynamic absorbers. In the case of cables, also crossties are sometimes used but they totally change the original characteristics of the system. Occasionally, these passive devices may not be sufficient and are then substituted by active or semi-active devices. All existing devices, including NES1, are based on the same principle: part of the kinetic energy is transferred from the structure to the device where it is dissipated. In the ELSA cable facility, a new strategy of vibration mitigation has been tested on taut cables of 45 meters length, attaching a unilateral spring perpendicularly to the cable near the anchorage. Tests of forced vibrations followed by a free decay have been carried out on the cable, with and without the spring. The proposed device appears to strongly modify the response of the cable and leads to a substantial reduction of the cable motions. Moreover, it drastically reduces the free decay period through a beating phenomenon. The tests have been repeated on two different cables and for two different spring materials (steel or SMA2). Because of its ability to change the cable dynamic properties through intermittent activation, this new passive device has been called “State Switched Inducer” (SSI). The multiplication and the coupling of the modes evident in the spectra are the main property responsible of the vibration mitigation effect. The positive effect of the hardening, which grows with the rate of non linearity on the original structure is also highlighted. This first large-scale experimental campaign shows that the SSI outperforms classical passive device opening the way to a new kind of smart and low cost vibration mitigation systems in such applications.

TIRELLI Daniel; 

2014-08-22

Hindawi

JRC82365

http://downloads.hindawi.com/journals/sv/2014/135767.pdf,    https://publications.jrc.ec.europa.eu/repository/handle/JRC82365,   

10.1155/2014/135767,