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CivilComp Proceedings
ISSN 17593433 CCP: 81
PROCEEDINGS OF THE TENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping
Paper 206
A Practical Approach to Install Viscous Dampers on Flexible Structures K. Engelen, J. Anthonis and H. Ramon
Laboratory for Agricultural Machinery and Processing, Catholic University Leuven, Belgium K. Engelen, J. Anthonis, H. Ramon, "A Practical Approach to Install Viscous Dampers on Flexible Structures", in B.H.V. Topping, (Editor), "Proceedings of the Tenth International Conference on Civil, Structural and Environmental Engineering Computing", CivilComp Press, Stirlingshire, UK, Paper 206, 2005. doi:10.4203/ccp.81.206
Keywords: viscous damper, vibration control, passive damping, flexible structure, spray boom, mast structure.
Summary
A simple methodology is developed to install viscous dampers on
flexible structures with low inherent damping in order to reduce
vibrations. Approximating formulas are derived for the maximum
attainable modal damping and corresponding optimal damping
constant at a given damper location. The potential and the
limitations of the methodology are demonstrated by two case
studies: damping of agricultural spray boom structures and damping
of mast structures.
Incorporating viscous dampers in flexible structures can be a very effective means of reducing unwanted vibrations. In doing so, two questions have to be answered: where are the dampers placed in the structure; and what are the optimal damping constants resulting in minimized vibrations? In the literature usually very complex algorithms are used to optimize damping constants, according to either an eigenvaluebased criterium or an energy criterium, starting from a discrete representation of the structure by its mass and stiffness matrix [1,2]. The damper position is rarely incorporated in the optimization procedure [3], despite the fact that this position is most critical. In this paper it is shown that finding a good damper location and optimal damping constant can be very easy in the case one single viscous damper is used to optimize the modal damping of one particular eigenmode. Simple approximating formulas are derived for the maximum attainable modal damping of the eigenmode and the corresponding optimal damping constant at a given damper location and where are the resonance frequencies of the structure, are the resonance frequencies of the structure with locked damper, and is the static stiffness of the structure at the damper location. These parameters are easily obtainable from a model of the structure constructed with commercial finite element software and they are also easily experimentally identifiable. The approximation is only valid when the eigenmodes of the structure are not significantly changed by locking the damper, which is for example the case when a relative damper is placed in a structure, or when an absolute damper is attached near the anchorage of a stay cable or near the clamping point of a mast structure. This is verified by numerical simulations and experiments in the two case studies: damping of agricultural spray booms and damping of mast structures. References
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