RESPUESTA DINÁMICA DE PLATAFORMAS DE PIERNAS TENSIONADAS ANTE OLEAJE IRREGULAR

Abstract

This document presents technical issues about the study of dynamic behavior of a Tension Leg Platform under the action of extreme ocean conditions such as wave sea states as well as ocean currents in the Golf of Mexico. Two main relevant subjects are included and described during the study, such as geometric non linear behavior imposed by the station keeping structural conditions (Tension legs) and the randomness of the ocean variables such as wave heights and current velocity which are the main source of dynamic forces acting on the platform. A mathematical model is developed along with the governing equations that describe the Platform-Solicitation dynamic behavior, and then applicable sea states are defined. Sea state definition is performed throw statistical estimations during a finite period, such sea states are commonly represented using wave spectral densities as functions of statistical parameters like significant wave height Hs and peak period Tp . The spectral densities are then converted into time series throw wave stochastic simulation adding multiple harmonic components from the spectrum. Once the metocean variables have been defined, the water particle kinematics around the platform components are used to generate dynamic forces over the entire platform hull and translating their effect in the platform gravity center getting the force vector time history which is imposed as input to solve the governing equations. The solution is performed step by step due to the fact that stiffness coefficients are non linear producing non constant structural natural frequencies. Finally, results about the dynamic response from a case of study are presented, such a case is an hypothetical Tension Leg Platform located somewhere in the south of the Golf of Mexico in a 1000 meter water depth.