Nonlinear dynamics of statically displaced tendons with non-conventional end conditions

Abstract

This study deals with the nonlinear dynamic behavior of TLP tendons subjected to heaving motions imposed at the top. It investigates a realistic configuration that is determined by static displacements and non-conventional boundary conditions defined by torsional springs attached at the end connections. Both considerations alter the characteristics of the tendon dynamics, both linear and nonlinear. The study is dedicated to the investigation of the dynamic impacts that could greatly affect tendon's structural integrity under severe loading. Two major issues are identified and examined: (i) possible tension cancellation and (ii) identification of the nonlinear internal resonances due to parametric-like excitation and analytical processing of the nonlinear system at relevant events. The whole process makes use of the complicated static configuration that takes into account the initial tendon displacement(s) and the boundary conditions determined by the existence of the torsional springs. The tension cancellation occurrences due to heavy vertical loading imposed at the top, are assessed by means of the numerical solution of the underlying boundary value problem. It is shown that the use of springs reduces the possibility for the nullification of the total tension and the destabilization of the floater which could be encountered under “ringing motions”. The identification of the internal resonances is implemented through the analytic processing of the reduced governing set, using perturbation analysis.