مطالعه تجربی اثرات موج‌گیر مربعی بر روی برش پایه حداکثر و لنگر واژگونی سازه جکت دریایی

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد مراغه، دانشگاه آزاد اسلامی، مراغه

2 گروه مهندسی عمران، واحد تبریز، دانشگاه آزاد اسلامی، تبریز

3 گروه آب، دانشکده مهندسی عمران، دانشگاه تبریز

چکیده

هدف از این تحقیق، به ­دست آوردن نیرویِ برش پایه و لنگر واژگونی جکتِ دریایی، در مواجهه با امواج تصادفی دریا و به ­کارگیری موج­گیر شناور مربعی شکل در جلوی سازه جکت، با هدفِ کاهش نیرو و لنگر واژگونی می ­باشد. در این راستا، مدل سازه جکت به ارتفاع 55/4 متر، ساخته و در فلوم آزمایشگاه ملّی دریایی شهدای خلیج فارس، به طول 402 متر و عمق ساکن آب 4 متر، در معرض امواج تصادفی دریا، تحت طیف جانسواپ (Jonswap)، قرار گرفت. موج ­گیر شناور با مقطع مربعی در جلویِ جکت، قرار گرفته و امواج تصادفی با ارتفاع موج 23 سانتی­ متر به جکت تابانده شد. نتایج مأخوذه نشان می ­دهد، موج ­گیر در امواج حداکثر، مؤثر و میانگین به­ ترتیب، 24/14، 67/24 و 57/8 درصد، کاهش برش پایه و 29/29، 78/19 و 71/23 درصد کاهش لنگر واژگونی را موجب شده است. در تمام آزمایش­ ها شرایط آب عمیق حاکم است.

کلیدواژه‌ها


عنوان مقاله [English]

Effects of Floating Wave Barriers with Square Cross Sections on the Wave-induced Forces Exerted to an Offshore Jacket Structure

نویسندگان [English]

  • Arash Dalili Osguei 1
  • Ramin Vafaeipoor 2
  • Ahmad Maleki 1
  • Hamid Ahmadi 3
1 Department of civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
2 Deapartment of Civil Engineering, Islamicazad University, Tabriz Branch, Iran
3 Faculty of Civil Engineering, University of Tabriz, Tabriz , Iran
چکیده [English]

The jacket-type platform is the most common offshore structure employed for the oil and gas production from the reservoirs below the seabed. It consists of three main parts: superstructure or topside, substructure or jacket, and the foundation or piles. Construction of floating breakwaters and wave barriers is one of the commonly used methods for the protection of harbors and coastal structures. However, their application for the protection of offshore structures has not been extensively studied. The present paper investigates the effects of a floating wave barrier installed in front of an offshore jacket structure on the wave height, wave-induced forces, and consequently jacket’s base shear and overturning moment.
Abul-Azm and Gesraha (2000) studied the hydrodynamics of floating pontoons under oblique waves. Gesraha (2006) analyzed the shaped floating breakwater in oblique waves. Rahman et al. (2006) presented a numerical modeling for the estimation of dynamic responses and mooring forces of submerged floating breakwaters. Christensen et al. (2018) conducted a set of experimental and numerical studies on floating breakwaters. Dong et al. (2008) carried out a number of experiments on the wave transmission coefficients of floating breakwaters.
In the present research, a jacket model with the height of 4.55m was fabricated and tested in wave flume of NIMALA marine laboratory. The wave flume was 402m long. The jacket was tested at the water depth of 4m subjected to JONSWAP waves with the height of 20cm, 23cm, and 28cm. The mechanism of wave energy dissipation due to hitting a wave barrier is mainly a combination of the wave diffraction and the wave reflection. A square cross section was selected for the wave barrier. Results showed that a floating wave barrier can effectively reduce the base shear and overturning moment in an offshore jacket structure.

کلیدواژه‌ها [English]

  • Jacket structure
  • Random Waves
  • Floating wave barrier
  • NIMALA flume
  • Base shear
  • Overturning Moment
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