Energy based optimization of viscous–friction dampers on cables

Abstract

This investigation optimizes numerically a viscous–friction damper connected to a cableclose to one cable anchor for fastest reduction of the total mechanical cable energy during afree vibration decay test. The optimization parameters are the viscous coefficient of theviscous part and the ratio between the friction force and displacement amplitude of thefriction part of the transverse damper. Results demonstrate that an almost pure frictiondamper with negligibly small viscous damping generates fastest cable energyreduction over the entire decay. The ratio between the friction force and displacementamplitude of the optimal friction damper differs from that derived from the energyequivalent optimal viscous damper. The reason for this is that the nonlinearity ofthe friction damper causes energy spillover from the excited to higher modes ofthe order of 10%, i.e. cables with attached friction dampers vibrate at severalfrequencies. This explains why the energy equivalent approach does not yield theoptimal friction damper. Analysis of the simulation data demonstrates that theoptimally tuned friction damper dissipates the same energy per cycle as if each modalcomponent of the cable were damped by its corresponding optimal linear viscousdamper.