Analisis Distribusi Tegangan Dan Umur Kelelahan Pada Extension Deck Leg Akibat Peninggian Deck Pasca Subsidence

Harianto, Eko Puji (2014) Analisis Distribusi Tegangan Dan Umur Kelelahan Pada Extension Deck Leg Akibat Peninggian Deck Pasca Subsidence. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Subsidence merupakan penurunan tanah dasar laut yang disebabkan oleh pembebanan berlebih atau pengambilan material-material dari dalam tanah yang berlebihan (minyak dan gas bumi). Pada anjungan lepas pantai yang sudah beroperasi lebih dari 30 tahun, penurunan tanah sangat mempengaruhi keberadaan struktur di atasnya. Untuk tetap aman berproduksi maka anjungan perlu ditinggikan melalui deck rising. Penelitian ini bertujuan untuk menganalisa distribusi tegangan dan umur kelelahan struktur tambahan pada deck leg anjungan lepas pantai yang mengalami peninggian pasca subsidence. Analisis berdasarkan studi kasus platform L-PRO yang beroperasi di Laut Jawa yang telah mengalami peninggian deck leg 4 meter dari kondisi awal. Analisa global struktur dilakukan menggunakan bantuan software GT-Strudl untuk mendapatkan gaya – gaya dan momen yang terjadi akibat beban aksial dari topside module yang disangga oleh deck leg dan gaya lateral dari beban lingkungan, yang kemudian menjadi inputan untuk analisis tegangan lokal menggunakan pendekatan Finite Element Analysis untuk mendapatkan Hot Spot Stress (HSS). Dengan HSS kemudian di plot ke dalam kurva S-N untuk mendapatkan nilai N, untuk selanjutnya dapat dihitung rasio kerusakan kumulatif (D) dan menentukan umur kelelahan struktur extension deck leg. Dari Finite Element Analysis didapatkan tegangan maksimum terjadi pada sambungan struktur upper cutting existing deck leg dan deck leg bushing sebesar 47961 psi. Nilai Hot Spot Stress (HSS) terbesar adalah pada tinggi gelombang 2,871 feet dengan arah datang gelombang 270 derajat sebesar 31506,04 psi. Dari penjumlahan masing – masing kondisi pembebanan didapatkan nilai rasio kerusakan kumulatif (D) total sebesar 0,010530632. Sehingga didapatkan umur kelelahan terkecil dari Finite Element Analysis selama 94 tahun dan umur operasi struktur selama 47 tahun. Yaitu pada sambungan las antara upper cutting deck leg dan deck leg bushing.
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Subsidence is the seabed soil degradation caused by excessive loading or taking materials from excessive soil (oil and gas). In the offshore platforms that have been operating for more than 30 years, the subsidence greatly affect the existence of structures on it. To stay safe production the platform should be raised through the deck raising. This study aims to analyze the stress distribution and fatigue life of the structure addition in the leg of the offshore platform decks were experiencing post-subsidence elevation. The analysis is based on case studies of L-PRO platform operating in the Java Sea that has undergone a deck leg elevation 4 feet from the initial conditions. Global analysis of the structure is done using software GT Strudl to get force and moment caused by the axial load of the topside modules are supported by the deck leg and lateral force of the load environment, which then becomes the input for local stress analysis using Finite Element Analysis approach to get the Hot Spot Stress (HSS). With HSS later in the plot to the SN curve to obtain the value of N, can then be calculated ratios for cumulative damage (D) and determine the fatigue life of the structure deck leg extension. Finite Element Analysis of the obtained maximum stress occurs at the junction of cutting the existing upper deck structure and deck leg leg bushings at 47 961 psi. Value Hot Spot Stress (HSS) is the largest at 2,871 feet high waves with wave direction 270 degrees at 31506.04 psi. From the sum of each loading condition, the total ratio of cumulative damage (D) was 0.010530632. The smallest fatigue life of Finite Element Analysis is about 94 years and operation life of the structure is 47 years. Located in the welded joint between the leg and the upper deck cutting deck bushing leg.

Item Type:	Thesis (Other)
Additional Information:	RSKe 627.98 Har a-2014
Uncontrolled Keywords:	Subsidence, platform LIMA, umur kelelahan, Hot Spot Stress (HSS), extension deck leg, fatigue life, Hot Spot Stress
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:	Mr. Marsudiyana -
Date Deposited:	23 Oct 2023 09:43
Last Modified:	23 Oct 2023 09:43
URI:	http://repository.its.ac.id/id/eprint/104845

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