Keywords: cables, vibration mitigation, passive control, magnetorheological damper, hysteresis models.

Structural cables are rapidly diffusing in the modern civil engineering for their valuable static, economic and aesthetical performances. Nonetheless, inherent flexibility and low damping properties cause concern regarding their vulnerability to high-amplitude oscillations, which can arise from a variety of dynamic excitation sources.

Among different available countermeasures, increasing interest is presently paid to different techniques of longitudinal and transversal control. In this respect, a promising application field regards the vibration mitigation of the bridge stay cables, includes both active, passive and, expecially, semi-active design strategies.

Applied research has been greatly focused in developing reliable and energy-saving passive control solutions, based on oil dampers, inter-stay cross ties, and, recently, hanging tuned mass dampers. Technical and economical difficulties are instead still limiting the field application of active cable control, although highly-performing longitudinal tendon strategies are nowadays founded on a well-established theoretical [1] and experimental background [2]. Within this framework, a potentially acceptable compromise among costs, reliability and effectiveness of the control scheme is provided by semi-active strategies.

Although the mitigation effect of transversal dampers on the cable oscillations has been investigated in the literature, starting from the work by Pacheco [3], the major research effort has been focused on enhancing the cable dynamical modelling, seeking approximate closed-form and complex-valued solutions of the system eigenproblem, or formulating advanced control algorithms. Minor attention has been instead devoted to investigate the coupled dynamics of the cable-damper system, including a reliable rheological model of the damper. Only a few recent studies take into account the hysteretic component in modelling the damper-cable interaction force, whereas the only viscous one is commonly considered.

In the present paper a monodimensional model is formulated for the transverse motion of taut cables, including geometric nonlinearities. The passive control action of a transversal magnetorheologic damper is introduced. Different rheological models (Bingham, Bouc-Wen) of the damper hysteretic behaviour, with an increasing number of control parameters, are considered. From the decomposition of the displacement field by means of Ritz-Rayleigh functions, and retaining the only rheological nonlinearities, a 4dof model is obtained.

Numerical solutions are presented with the aim of reproducing the experimental data measured on a laboratory-scaled physical model during free oscillation tests. Satisfying agreement is globally achieved, since a good matching is obtained in reproducing the measured control performances of the passive damper, and in particular the analytical model qualitatively captures the clamping damper effect observed for low-tensioned cables. The relative effectiveness of the Bingham and Bouc-Wen damper models is also discussed.

1

Gattulli V., Vestroni F., Nonlinear strategies for longitudinal control in the stabilization of an oscillating suspended cable, Dynamics & Control, 10(4), 359-374, 2000. doi:10.1023/A:1011273600500

2

Fujino Y., Susumpow P., An experimental study on active control of in-plane cable vibration by axial support motion, Earthquake Engineering & Structural Dynamics, 23(12), 1283-1297, 1994. doi:10.1002/eqe.4290231202

3

Pacheco B.N., Fujino Y., Sulekh A., Estimation curve for modal damping in stay cables with viscous damper, J. Structural Engineering, 119(6), 1961-1979, 1993. doi:10.1061/(ASCE)0733-9445(1993)119:6(1961)

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £120 +P&P)