Analisis Ultimate Strength pada Conductor Supported Wellhead Platform Berbasis Keandalan akibat Beban Gempa Pasca Subsidence

Pattinasarany, Fergrini Lefranzy (2026) Analisis Ultimate Strength pada Conductor Supported Wellhead Platform Berbasis Keandalan akibat Beban Gempa Pasca Subsidence. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Subsidence merupakan peristiwa penurunan tanah yang disebabkan oleh beberapa faktor, salah satu contohnya adalah pengambilan material dari dalam tanah secara berlebihan, seperti minyak dan gas bumi. Pada struktur anjungan lepas pantai yang beroperasi untuk kebutuhan eksploitasi migas, peristiwa subsidence sangat rentan terjadi dan akan mempengaruhi keberadaan struktur diatasnya. Oleh karena itu, pada penelitian ini membahas analisis kekuatan ultimate dan keandalan struktur Conductor Supported Wellhead Platform milik sebuah perusahaan. Analisis ultimate dilakukan dengan pendekatan non-linear pushover dengan beban seismik diberikan secara bertahan (incremental). Hasil dari analisis seismik menunjukkan bahwa semakin dalam subsidence berdampak pada naiknya unity check (UC) pada struktur saat kondisi Extreme Level Earthquake (ELE) dengan UC maksimum 0,41 dan Abnormal Level Earthquake (ALE) dengan UC maksimum 0,62. Kemudian hasil analisis pushover menunjukkan bahwa Reserve Strength Ratio (RSR) dan System Redundancy (SR) akibat beban seismik cenderung menurun seiring bertambahnya kedalaman subsidence. Dengan kondisi RSR terkritis pada kondisi ALE arah beban X subsidence 11,5 m sebesar 2,36. Analisis keandalan menggunakan simulasi monte carlo pada kondisi ALE kedalaman subsidence maksimum arah beban X dan beban Y memperoleh indeks keandalan masing masing sebesar 5,85 dan 6,46. Hal ini menunjukkan struktur masih berada dalam batas aman terhadap beban gempa walaupun terjadi subsidence.
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Subsidence is a ground settlement phenomenon caused by several factors, one of which is excessive extraction of subsurface materials such as oil and gas. In offshore platform structures operating for hydrocarbon exploitation, subsidence is highly likely to occur and can significantly affect the integrity of the structure above. Therefore, this study focuses on the analysis of ultimate strength and structural reliability of a Conductor Supported Wellhead Platform owned by a company. Ultimate strength analysis was conducted using a nonlinear pushover approach, in which seismic loads were applied incrementally. The seismic analysis results indicate that increasing subsidence depth leads to an increase in the unity check (UC) values of the structure under Extreme Level Earthquake (ELE) and Abnormal Level Earthquake (ALE) conditions, with maximum UC values of 0.41 and 0.62, respectively. Furthermore, the pushover analysis results show that the Reserve Strength Ratio (RSR) and System Redundancy (SR) under seismic loading tend to decrease as the subsidence depth increases. The most critical RSR condition was observed under ALE loading in the X-direction at a subsidence depth of 11.5 m, with an RSR value of 2.36. Reliability analysis using Monte Carlo simulation under ALE conditions at the maximum subsidence depth in both X and Y loading directions resulted in reliability indices of 5.85 and 6.46, respectively. These results indicate that the structure remains within acceptable safety limits against seismic loading despite the occurrence of subsidence.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Conductor Supported Platform, Pushover, Seismic, Subsidence, Monte Carlo
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User:	Fergrini Lefranzy Pattinasarany
Date Deposited:	20 Jan 2026 02:39
Last Modified:	20 Jan 2026 02:51
URI:	http://repository.its.ac.id/id/eprint/129763

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