Hibatullah, Marsanura (2018) Analisis Kelelahan Struktur Steel Catenary Riser akibat Vortex Induced Vibration dan Pergerakan Semisubmersible. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Riser didefinisikan sebagai segmen vertikal (mendekati vertikal) pipa yang menghubungkan fasilitas di atas air dengan jaringan pipa bawah laut. Riser akan mendapatkan gaya hidrodinamis yang bersifat siklik. Gaya yang bekerja terus menerus pada riser akan mengakibatkan suatu kelelahan yang menyebabkan kegagalan fatigue. Fatigue merupakan salah satu kriteria desain yang harus diperhitungkan dalam proses desain struktur. Dalam Laporan Tugas Akhir ini dibahas fatigue analysis akibat pergerakan floater yaitu 1st Order wave loads dan 2nd Order wave drift, dan juga akibat fenomena Vortex Induced Vibration yang terjadi pada riser tipe Steel Catenary Riser di suatu Semi-Submersible yang beroperasi di laut Natuna. Studi dilakukan dengan membuat model struktur Semi-Submersible dan riser lalu disimulasikan menggunakan perangkat lunak analisis dinamik. Analisis fatigue dilakukan dengan pendekatan Kurva S-N dan mengacu pada DNV RP F204 “Riser Fatigue” dan DNV RP C203 “Fatigue Design of Steel Structure”. Hasil analisis menunjukkan bahwa 1st order wave loads memberikan dampak paling besar pada tension dan bending moment SCR,. Tegangan Nominal rata-rata terbesar terjadi pada bagian flex joint di titik arc length 0 m arah 90º sebesar 72,253 MPa dan titik ini yang dijadikan sebagai titik tinjau untuk analisa fatigue. Hasil perhitungan fatigue menunjukan bahwa umur yang fatigue sebesar 74,5 tahun yang mana sesuai dengan umur yang direncanakan yaitu 20 tahun.
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A riser is the nearly – vertical segment of pipe which connects the offshore facilities with subsea pipes and installations. Risers are subject to cyclic hydrodynamic loads. The forces that continuously work on risers cause fatigue damage which cause fatigue failure. Fatigue is a design criterion which must be considered in the structure design process. In this research, fatigue analysis due to 1st and 2nd order floater motions and Vortex Induced Vibration is investigated on the Steel Catenary Riser of a Semi – Submersible operating in the Natuna Sea. The study models a semi – submersible structure and risers and is simulated using a dynamic analysis software. Fatigue analysis is carried out with S-N curve approach referring to DNV RP F204 “Riser Fatigue” and DNV RP C203 “Fatigue Design of Steel Structure”. The analysis results show that 1st order floater motions have the biggest effect on tension and bending moment on the Steel Catenary Riser. The biggest mean nominal stress of 72,253 MPa occurs at flex joint arc length 0 m at 90o and this point is used for the fatigue analysis. The results of fatigue damage calculation show that the fatigue life of 74,5 years is suitable for the design life.
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Uncontrolled Keywords: | Steel Catenary Riser, Fatigue Damage, Semisubmersible Motion, Rainflow Counting, Vortex Induced Vibration |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA418.38 Materials--Fatigue. T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures |
| Divisions: | Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis |
| Depositing User: | Marsanura Hibatullah |
| Date Deposited: | 28 Jun 2021 02:59 |
| Last Modified: | 28 Jun 2021 02:59 |
| URI: | http://repository.its.ac.id/id/eprint/55399 |
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