Analisis Integritas Kekuatan Struktur Jacket Platform Eksisting Empat Kaki Akibat Modifikasi Extension Deck

Girsang, John Lihardo (2026) Analisis Integritas Kekuatan Struktur Jacket Platform Eksisting Empat Kaki Akibat Modifikasi Extension Deck. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Anjungan lepas pantai tipe jaket (Jacket Platform) merupakan infrastruktur vital dalam industri minyak dan gas yang seringkali memerlukan modifikasi, seperti perluasan dek (extension deck), untuk memenuhi kebutuhan operasional baru. Penambahan struktur ini berdampak pada perubahan distribusi beban yang berpotensi memengaruhi integritas kekuatan secara keseluruhan. Penelitian ini bertujuan untuk menganalisis integritas kekuatan struktur pada platform eksisting empat kaki sebelum dan sesudah modifikasi perluasan dek, mengevaluasi kekuatan batas melalui analisis pushover, serta menghitung laju perambatan retak pada titik sambungan (tubular joint) paling kritis. Metode elemen hingga digunakan untuk mengevaluasi respons struktural. Analisis global dilakukan melalui pemodelan in-place menggunakan perangkat lunak SACS untuk mengidentifikasi nilai Unity Check (UC) elemen struktur terhadap kombinasi beban operasi dan lingkungan. Selanjutnya, analisis pushover dilakukan untuk mengetahui cadangan kekuatan maksimum (Reserve Strength Ratio/RSR) saat struktur menerima pembebanan ekstrem hingga batas keruntuhannya. Berdasarkan hasil analisis global tersebut, sambungan paling kritis ditinjau lebih lanjut menggunakan analisis lokal dengan perangkat lunak ANSYS. Retakan awal (initial crack) dengan profil semi-elliptical dimodelkan pada titik kritis untuk menghitung Stress Intensity Factor (SIF). Laju perambatan retak (crack propagation rate) kemudian dikalkulasi menggunakan prinsip Linear Elastic Fracture Mechanics (LEFM) yang berdasar pada Hukum Paris-Erdogan. Hasil analisis in-place menunjukkan bahwa integritas struktur tetap memenuhi standar keselamatan pasca-modifikasi, dengan nilai UC maksimum tercatat sebesar 0,85 (UC < 1,0) pada elemen 401-404L. Pada evaluasi pushover, struktur modifikasi memiliki kapasitas disipasi energi yang memadai dengan nilai RSR terendah sebesar 3,401 pada arah pembebanan 90°. Pada evaluasi lokal di sambungan kritis 404L, laju pertumbuhan retak terhitung sebesar 5,4034E-11 in/cycle. Penelitian ini mengonfirmasi bahwa platform eksisting memiliki kapasitas kelayakan struktural dan cadangan kekuatan yang aman untuk terus beroperasi setelah modifikasi perluasan dek dilakukan.
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Jacket platforms are vital infrastructures in the oil and gas industry that often require modifications, such as deck extensions, to meet new operational demands. The addition of this structure impacts the load distribution, which potentially affects the overall structural strength integrity. This research aims to analyze the structural strength integrity of an existing four-legged platform before and after a deck extension modification, evaluate the ultimate strength through a pushover analysis, and calculate the crack propagation rate at the most critical tubular joint. The finite element method was used to evaluate the structural response. A global analysis was conducted through in-place modeling using SACS software to identify the Unity Check (UC) values of the structural elements under a combination of operational and environmental loads. Furthermore, a pushover analysis was performed to determine the maximum reserve strength (Reserve Strength Ratio/RSR) when the structure is subjected to extreme loading up to its collapse limit. Based on the global analysis results, the most critical joint was further examined using local analysis with ANSYS software. An initial crack with a semi-elliptical profile was modeled at the critical point to calculate the Stress Intensity Factor (SIF). The crack propagation rate was then calculated using the principles of Linear Elastic Fracture Mechanics (LEFM) based on the Paris-Erdogan Law. The in-place analysis results indicate that the structural integrity continues to meet safety standards post-modification, with a maximum UC value recorded at 0.85 (UC < 1.0) on member 401-404L. In the pushover evaluation, the modified structure demonstrated adequate energy dissipation capacity, with the lowest RSR value being 3.401 in the 90° loading direction. In the local evaluation at critical joint 404L, the crack growth rate was calculated at 5.4034E-11 in/cycle. This study confirms that the existing platform possesses the structural feasibility and safe reserve strength capacity to continue operations after the deck extension modification is implemented.

Item Type:	Thesis (Other)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA645 Structural analysis (Engineering)
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User:	John Lihardo Girsang
Date Deposited:	29 Jul 2026 04:18
Last Modified:	29 Jul 2026 04:18
URI:	http://repository.its.ac.id/id/eprint/137827

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