Analisis Kelelahan Struktur Jacket 4 Kaki Akibat Pertumbuhan Marine Growth

Sambhala, Daniel (2025) Analisis Kelelahan Struktur Jacket 4 Kaki Akibat Pertumbuhan Marine Growth. Other thesis, Sepuluh Nopember Institute of Technology.

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Abstract

Struktur jacket empat kaki pada anjungan lepas pantai rawan mengalami kelelahan akibat pembebanan lingkungan, terutama akibat pertumbuhan marine growth di zona percikan (splash
zone). Pertumbuhan marine growth yang melebihi batas desain dapat meningkatkan diameter member tubular, menambah massa hidrodinamik, dan memperbesar gaya gelombang, yang pada akhirnya meningkatkan beban struktur. Penelitian ini bertujuan untuk menganalisis dampak pertumbuhan marine growth terhadap kelelahan struktur platform jacket WHP-A yang telah beroperasi selama 15 tahun. Analisis dilakukan melalui pemodelan dua kondisi struktur: model eksisting dengan dent dan marine growth, serta model inisial tanpa keduanya. Hasil analisis in-place menunjukkan bahwa nilai Unity Check (UC) tertinggi pada model eksisting mencapai 2,77, sedangkan pada model inisial hanya 0,62. Analisis kelelahan dilakukan dengan dua pendekatan. Metode cumulative damage menunjukkan bahwa fatigue life pada member chord 7366-1535 menurun drastis dari 137,97 tahun (model inisial) menjadi 10,23 tahun (model eksisting), dan pada member brace 7366-7369 dari 442,53 tahun menjadi 31,69 tahun— penurunan >92%. Metode fracture mechanics menggunakan Paris Law dan simulasi XFEM serta FEM menunjukkan umur kelelahan member dented 723M-1186 adalah 26,6 tahun, memenuhi target service life (25 tahun) namun tidak memenuhi design life (50 tahun) dengan Safety Factor 2. Hasil studi menegaskan bahwa keberadaan marine growth dan dent berpengaruh signifikan dalam menurunkan umur kelelahan struktur serta meningkatkan risiko kegagalan lokal, yang lebih akurat terdeteksi melalui pendekatan fracture mechanics dibandingkan metode cumulative damage konvensional.
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Four-legged jacket structures used in offshore platforms are vulnerable to fatigue due to environmental loading, particularly from marine growth in the splash zone. Excessive marine growth increases the diameter of tubular members, hydrodynamic mass, and wave forces, thus elevating structural stress. This study investigates the effect of marine growth on the fatigue life of the WHP-A jacket platform, which has been operating for 15 years. Two structural models were analyzed: an existing model with dent and marine growth, and an initial model without them. In-place analysis results showed the highest Unity Check (UC) value was 2.77 for the existing model, compared to only 0.62 for the initial model. Fatigue analysis was conducted using two approaches. The cumulative damage method revealed a severe reduction in fatigue life for chord member 7366-1535, from 137.97 years (initial) to 10.23 years (existing), and for brace member 7366-7369, from 442.53 years to 31.69 years—both showing >92% degradation. The fracture mechanics method using Paris Law and XFEM simulation found that the fatigue life of the dented member 723M-1186 was 26.6 years, meeting the 25- year service life but falling short of the 50-year design life under a Safety Factor of 2. The results highlight that marine growth and dent significantly reduce fatigue life and increase the risk of local failure, better captured by fracture mechanics analysis than by conventional cumulative damage approaches.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Jacket Platform Marine growth, inplace, cummulative dammage, fracture mechanics
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User:	Flavio Klorus Daniel Sambhala
Date Deposited:	21 Jul 2025 02:20
Last Modified:	21 Jul 2025 02:20
URI:	http://repository.its.ac.id/id/eprint/120220

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