VIBRATION REDUCTION IN STEEL CATENARY RISERS BY THE USE OF VISCOELASTIC MATERIALS

The increasing need for petroleum is leading to an exploration in waters each time deeper, leading the structures to have a complex behavior. One of the main components in this area are the risers. These structures are submitted to dynamic loads, among them, it can stand out the one that it is induced by the detachment of vortexes when the structure is submitted to sea currents. These loads may reduce their lifetime due to fatigue. Therefore, many methodologies are being developed to increase the damping of the risers and reduce the vibration effects. One of the ways to reduce the vibrations is the use of viscoelastic materials associated with constraining layers, known in literature as "sandwich structures". One possible application for this concept is related to the control and the reduction of vibrations in steel catenary risers. The main purpose of this work is present a methodology in order to increase the structural damping factors using the concept of sandwich structures with viscoelastic materials. This application differs from the usual because offshore structures work in lower frequencies than the civil ones, leading the need of an own development for its application. It was developed a numerical model of the sandwich tubes, and its results are evaluated through experimental tests in simple structures accomplished at the Structures Laboratory at COPPE/UFRJ. Through this analysis it is observed a great addition of damping that would allow a reduction of the vibration levels and an increase of the structures lifetime, for example, in steel catenary risers.