Analisis Perambatan Retak pada Sambungan Tubular Joint di Jacket Offshore Platform

Toyib, Aditya Wasista (2025) Analisis Perambatan Retak pada Sambungan Tubular Joint di Jacket Offshore Platform. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Struktur lepas pantai banyak digunakan untuk mendukung eksplorasi dan produksi minyak dan gas bumi, namun rentan mengalami kegagalan akibat fatigue, khususnya pada sambungan tubular yang menjadi titik konsentrasi tegangan akibat pengaruh geometri dan pembebanan siklik. Hasil analisis menunjukkan bahwa struktur mengalami pembebanan siklik sebesar 6.750.000 siklus per tahun dengan dominasi gelombang berperiode 4,6 detik. Dua pendekatan digunakan untuk memperkirakan umur kelelahan, yaitu cummulative damage berbasis SN-Curve dan fracture mechanics berbasis propagasi retak. Pendekatan cummulative damage menunjukkan bahwa pada kondisi splash zone terjadi variasi tegangan dari 34,98 Mpa hingga 334,91 Mpa menghasilkan stress range sebesar 229,93 MPa dan memprediksi umur kelelahan selama 22,75 tahun, sedangkan pendekatan fracture mechanics menghasilakan umur 18,98 tahun. Konsentrasi tegangan tertinggi teridentifikasi pada area weld toe sisi brace, khususnya di zona saddle brace, dimana kondisi plane stress pada sambungan tubular tipis mendorong perambatan retak lateral yang semakin signifikan seiring bertambahnya jumlah siklus. Hasil ini menegaskan pentingnya pemilihan pendekatan evaluasi kelelahan yang tepat untuk menjamin keandalan struktur dalam jangka panjang.
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Offshore structures are widely used to support oil and gas exploration and production activities; however, they are vulnerable to fatigue-induced failure, particularly at tubular joints, which often experience high stress concentrations due to geometric discontinuities and cyclic loading. The analysis indicates that the structure is subjected to approximately 6,750,000 wave-induced load cycles annually, dominated by wave periods of 4.6 seconds. Two approaches were employed to estimate the fatigue life: the cumulative damage method based on the SN-curve and the fracture mechanics approach based on crack propagation analysis. The cumulative damage approach revealed that, in the splash zone, stress varies from 34.98 MPa to 334.91 MPa, resulting in a stress range of 229.93 MPa and predicted a fatigue life of 22.75 years, whereas the fracture mechanics approach estimated a shorter fatigue life of 18.98 years. The highest stress concentration was observed at the weld toe of the brace, particularly in the saddle brace region, where the plane stress condition in thin-walled tubular joints promotes lateral crack propagation, which becomes increasingly significant with additional load cycles. These findings highlight the importance of selecting an appropriate fatigue evaluation method to ensure long-term structural reliability.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Perambatan Retak, Cumulative Damage, Fracture Mechanics, Sambungan Tubular, Kelelahan, Crack Propagtion, Tubular Joint, Fatigue.
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC1665 Offshore structures--Materials. T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures
Divisions:	Faculty of Marine Technology (MARTECH) > Offshore Engineering > 54040-(S1) Undergraduate Thesis
Depositing User:	Aditya Wasista Toyib
Date Deposited:	24 Jul 2025 05:05
Last Modified:	24 Jul 2025 05:05
URI:	http://repository.its.ac.id/id/eprint/121191

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