Controle de vibrações por sistema de atrito seco variável aplicado em cabos de pontes estaiadas

Abstract

The present work proposes to study the dry friction mechanism to control vibrations in cablestayed bridge cables. For this purpose, the finite element method was used to implement the cable model and its accuracy was obtained by applying the so-called vibrating string theory. In the modal analysis, the first five natural frequencies of the system under study were considered and the frequency response of the cable was analyzed for free vibration and with the proportional damping obtained by the Rayleigh method. Newmark’s method with average acceleration was used for numerical integration of the nonlinear ordinary differential system and, when necessary, modified by Newton-Raphson’s method. Linear, quadratic and cubic variations of dry friction as a function of displacement were analyzed, where the characteristics of each one and their influence on the responses were detailed. The use of two dampers was also analyzed, observing the influence of mechanical energy transfers to higher vibration modes on their efficiency. Through the numerical results it was possible to illustrate the linear variation efficiency of the friction force as a displacement function and the importance of considering the differences between damping by dry friction and its equivalent viscous damping.