Study of Offshore Jacket Platform Attached With Tuned Liquid Column Gas Damper

Abstract

With increase in need of energy, scarcity of natural resources also increases. Need for energy has led the people to move into the ocean since they contain abundant natural resources. Offshore platforms play a major role in exploring and exploiting these resources. Jacket platform being a fixed offshore jacket platform is used in water depths 300 to 400 m. The study of behavior of these offshore structures is vital part in the design since they are subjected to dynamic loading of waves, wind, earthquake, ice etc. These structures in hostile environment are subjected to heavy loads. There is need for controlling the response of these structures. This can be achieved by providing external dampers. There are various dampers available to control the response of structures. Tuned liquid dampers (TLD)s and Tuned Liquid Column Damper (TLCD)s use liquid inside to tune its frequency to natural frequency of structure. Tuned Liquid Column Gas Damper (TLCGD) is latest version of dampers. It has a unique flexibility of tuning frequency compared to all other dampers. In the present study, jacket platform is modeled as Multi degree of freedom (MDOF) system. At later stage, for simplistic analysis, MDOF system is reduced to SDOF system using static condensation. Performance of TLCGD for both the systems is compared. Airy’s wave theory is used for wave force excitation. Equations of motions for Jacket platform models attached with TLCGD are developed and solved using Newmarks β method in MATLAB. TLCGD is found to be very flexible in tuning the frequency and maximum reductions in response, 21.3% and 23.14% are observed at 0.3 MPa for MDOF and SDOF systems respectively. Work done shows that the results for MDOF and SDOF are comparable and hence, jacket as SDOF can be used for analysis for reducing the complexities.