Investigating the Effects of Combined Tuned Liquid Damper (CTLD) on Dynamic Behavior of Offshore Jacket-Type Platforms

Authors

1 Faculty of Civil Engineering, University of Tabriz

2 Faculty of Civil Engineering, Iran University of Science and Technology

Abstract

In the present paper, the efficiency of combined tuned liquid damper (CTLD) in controlling the dynamic responses of offshore jacket platforms under the earthquake and sea wave excitation is investigated. This type of damping system consists of one or more tanks containing a fluid, generally water or oil, which can be installed on the topside (superstructure) of the platform. During the excitation, hydrodynamic action induced by the sloshing of the water in the tank acts as a resistant force against the vibration and controls the structural response. In fact, due to the oscillation of the structure, the fluid inside the tank begins to oscillate in the opposite direction. During this process, most part of the fluid has a wave-like oscillatory motion, while the part adjacent to the tank’s floor experiences a rigid-type displacement and exerts impact pressures to the tank’s walls. In order to attain maximum decrease in the structural response, the oscillation frequency of the fluid inside the tank should be near the natural frequency of the structural free vibration which can be determined by performing a modal analysis. Hence, one of the objectives of the present study is to adjust the frequency of fluid’s oscillation based on the natural frequency of the jacket structure. In other words, the aim is to find a frequency range in which the maximum decrease can be achieved in the amplitude of structural responses. In this research, using the FE software ANSYS, a jacket-type platform having dimensions appropriate for the Persian Gulf climate (case study: SPD1 platform) was modeled and then dynamically analyzed by the modal and time-history approaches subjected to the records of El Centro and Tabas earthquakes as well as 10 cases of wave loading with different height and period. The CTLD system was optimally designed and after the verification of FE results, the dynamic responses of the jacket-type platform with and without CTLDs were compared.

Keywords


تفاخر ح، "بررسی رفتار دینامیکی سکوهای فراساحلی شابلونی مجهز به سیستم میراگر مایع تنظیم شده (TLD) تحت تحریک لرزه‌ای"، پایان‌نامه کارشناسی ‌ارشد، دانشکده مهندسی عمران، دانشگاه تبریز، 1392.
Al-Saif KA, Aldakhan KA, Foda MA, “Modified liquid column damper for vibration control of structures”, International Journal of Mechanical Sciences, 2011, 53 (7), 505-512.
American Petroleum Institute (API), “Recommended practice for planning, design and constructing fixed offshore platforms-working stress design (RP2A-WSD)”, 21th Edition, Washington DC, US, 2000.
Bargi Kh, Hosseini SR, Tadayon MH, Sharifian H, “Seismic response of a typical fixed jacket-type offshore platform (SPD1) under sea waves”, Open Journal of Marine Science, 2011, 1 (2), 36-42.
Chatterjee T, Chakraborty S, “Vibration mitigation of structures subjected to random wave forces by liquid column dampers”, Ocean Engineering, 2014, 87, 151-161.
Di Mateo A, Lo Iacono F, Navarra G, Pirrotta A, “Direct evaluation of equivalent linear damping for TLCD systems in random vibration for pre-designing purpose”, International Journal of Nonlinear Mechanics, 2014, 63, 19-30.
Frandsen JB, “Numerical prediction of tuned liquid tank structural systems”, Journal of Fluids and Structures, 2005, 20 (3), 309-329.
Housner GW, “Dynamic pressures on accelerated fluid containers”, Bulletin of the Seismological Society of America, US, 1957.
Jin Q, Li X, Sun N, Zhou J, Guan J, “Experimental and numerical study on tuned liquid dampers for controlling earthquake response of jacket offshore platform”, Marine Structures, 2007, 20 (4), 238-254.
Lee H, “Stochastic analysis for offshore structures with added mechanical dampers”, Ocean Engineering, 1997, 24 (9), 817-834.
Lotfollahi-Yaghin MA, Ahmadi H, Tafakhor H, “Seismic response of an offshore jacket-type platform incorporated with tuned liquid dampers”, Advances in Structural Engineering, 2016, 19 (2), 227-238.
Love JS, Tait MJ, “A preliminary design method for tuned liquid dampers conforming to space restriction”, Engineering Structures, 2012, 40, 187-197.
Marivani M, Hamed MS, “Numerical simulation of structure response outfitted with a tuned liquid damper”, Computers & Structures, 2009, 87 (17-18), 1154-1156.
Sun LM, Fujino Y, Pacheco BM, Chaiseri P, “Modelling of tuned liquid damper (TLD)”, Journal of Wind Engineering and Industrial Aerodynamics, 1992, 43(1-3), 1883-1894.
Tamura Y, Fuji K, Ohtsuki T, Wakahara T, Kohsaka R, “Effectiveness of tuned liquid dampers under wind excitation”, Engineering Structures, 1995, 17 (9), 609-621.
Vandiver JS, Mitome S, “Effect of liquid storage tank on the dynamic response of offshore platforms”, Applied Ocean Research, 1978, 1 (2), 67-74.
Wakahara T, Ohyama T, Fuji K, “Suppression of wind-induced vibration of a tall building using tuned liquid damper”, Journal of Wind Engineering and Industrial Aerodynamics, 1992, 43 (1-3), 1895-1906.
Warnitchai P, Pinkaew T, “Modelling of liquid sloshing in rectangular tanks with flow dampening devices”, Engineering Structures, 1998, 20 (7), 593-600.
Wu GX, Ma QW, Eatock Taylor R, “Numerical simulation of sloshing waves in a 3D tank based on finite element method”, Applied Ocean Research, 1998, 20 (6), 337-355.