Sari, Bunga Septya Winata (2015) Analisis Kekuatan Ultimate Berbasis Resiko Pada Struktur Jacket Wellhead Tripod Platform Akibat Terjadinya Scouring. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Banyak struktur lepas pantai terpancang yang mengalami keruntuhan
akibat scouring yang sangat ekstrim terletak di bagian pondasinya. Scouring yang
terjadi seringkali mempengaruhi integritas struktur yang mengakibatkan
kegagalan konstruksi karena gaya yang diterima jacket leg semakin besar. Oleh
karena itu, analisis dampak scouring yang berakibat penurunan kekuatan struktur
secara keseluruhan hingga keruntuhan perlu dilakukan, kerana struktur sudah
berbeda dari rancangan awal. Pada tugas akhir ini dilakukan analisis resiko pada
jacket wellhead tripod platform UL A PHE ONWJ dalam kondisi ultimate dengan
variasi kedalaman scouring. Analisis ultimate dilakukan dengan meningkatkan
beban lingkungan kondisi badai secara bertahap hingga struktur mengalami
keruntuhan karena terbentuknya member-member pada keadaan plastis. Member
dengan plastisitas 100% digunakan dalam analisis keandalan, dimana peluang
kegagalannya diperoleh dengan simulasi Monte Carlo yang meggunakan Random
Number Generator (RNG). Sedangkan, keandalan sistem diperoleh dengan
metode Reliabilty Block Diagram (RBD) yang selanjutnya digunakan dalam
analisis resiko. Berdasarkan analisis kekuatan struktur diperoleh kedalaman
scouring maksimum agar tetap memenuhi ISO 19902 adalah kedalaman scouring
15 ft dengan unity check of member terbesar mencapai 0.9752. Pada analisis
keruntuhan diperoleh hasil Reserve Strength Ratio (RSR) terkecil 5,474 dengan
kondisi scouring 17,5 ft akibat arah pembebanan 300. Analisis keandalan sistem
dilakukan untuk kondisi non scouring hingga kondisi scouring 10 ft dengan
keandalan terkecil mencapai 0,99998 dan PoF terbesar 1,74485x10-5. Berdasarkan
matriks resiko didapatkan hasil bahwa platform UL A PHE ONWJ saat kondisi
scouring 10 ft memiliki resiko rendah untuk konsekuensi safety, sedangkan
konsekuensi environment memiliki resiko tinggi, serta konsekuensi business
berada di area medium risk yang merupakan daerah as low as reasonably
practicable (ALARP).
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Many fixed offshore structures collapses due to extreme scouring located
at the foundation. Mostly the scour make an impact to the integrity of structures
that lead to the failure of construction due the received force to jacket leg.
Therefore, scouring analysis that a commodates scouring, collapse analysis need
to be done, because the structure is different from initial design. Risk analysis in
this final project will be done on UL A PHE ONWJ tripod jacket wellhead
platform in the ultimate conditions with scouring depth variations. Ultimate
analysis is done by increasing gradually the environmental strorm condition until
structure collapse due to the deformation of the members in to plastic condition.
Member with 100% plasticity is used in the system reliability analysis, where the
probabilty of failure are obtained using Monte Carlo simulations. Whereas, the
reliability of the system obtained by the Reliabilty Block Diagram (RBD) method,
are then used in the risk analysis. Based on structural strength analysis, the result
of maximum scouring depth in order to comply with ISO 19902 standard is 15 ft
depth of scouring, with the largest unity check of member reaches 0,9752. On the
collapse analysis, the result of smallest RSR is 5,474 with the scouring condition
17,5 ft due to loading direction 300. The system reliabity analysis was done for
non-scouring condition until 10 ft scouring condition with the smallest reliability
reaches 0,99998 and the largest probability of failure is 1,74485x10-5. Based on
the risk matrix the result of UL A PHE ONWJ Platform, scouring condition 10 ft
has a low risk for the safety consequence. Whereas, the consequence of
environment has a high risk, and then the consequence of business are at medium
risk area which is in the area of as low as reasonably practicable (ALARP).
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Additional Information: | RSKe 627.98 Sar a |
| Uncontrolled Keywords: | ALARP, Monte Carlo, Reliabilty Block Diagram, Scouring, Ultimate |
| 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: | Yeni Anita Gonti |
| Date Deposited: | 19 Feb 2020 06:43 |
| Last Modified: | 19 Feb 2020 06:43 |
| URI: | http://repository.its.ac.id/id/eprint/75041 |
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