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All Journal REKAYASA Journal of Science and Applicative Technology IJOCE (International Journal of Offshore and Coastal Engineering) Zona Laut : Jurnal Inovasi Sains dan Teknologi Kelautan Indonesian Community Journal Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse) Jurnal Pengabdian Sosial TeknoKreatif: Jurnal Pengabdian kepada Masyarakat
Nafisa Nandalianadhira
Institut Teknologi Sumatera
Religion Aerospace Engineering Agriculture, Biological Sciences & Forestry Civil Engineering, Building, Construction & Architecture Computer Science & IT Control & Systems Engineering Decision Sciences, Operations Research & Management Earth & Planetary Sciences Economics, Econometrics & Finance Education Electrical & Electronics Engineering Energy Engineering Environmental Science Industrial & Manufacturing Engineering Law, Crime, Criminology & Criminal Justice Materials Science & Nanotechnology Mechanical Engineering Physics Public Health Social Sciences Transportation Other

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Journal : rekayasa

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Studi Komparasi Stabilitas Pipa Bawah Laut dengan DNVGL-RP-F109 dan Elemen Hingga Nafisa Nandalianadhira; Mochammad Fathurridho Hermanto
Rekayasa Vol 16, No 2: Agustus 2023
Publisher : Universitas Trunojoyo Madura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21107/rekayasa.v16i2.18804

Abstract

Deployment under the sea without being excavated or buried is the most effective alternative. The subsea pipeline must be ensured to be stable on the seabed, not experiencing movement when exposed to environmental forces. There are two main things that must be analyzed in the design process and stability analysis of subsea pipelines, hydrodynamic and hydrostatic forces. In the subsea pipeline design process, one of the most important steps is determining the wall thickness. One standard that is widely used is DNVGL-ST-F101. The diameter and thickness of the subsea pipeline are important parameters for determining subsea pipeline stability. The relationship between the forces acting to the subsea pipeline and the resistance of the soil (seabed) has been regulated in DNVGL-RP-F109. In addition, stability calculations can also be performed based on subsea pipeline modeling on the seabed using the finite element method. Based on these two methods, the vertical and lateral stability of the subsea pipeline can be determined. If the subsea pipeline is unstable, it is necessary to add concrete coating. Based on the pipe properties and environmental data, the wall thickness of the subsea pipeline is 18.203 mm. To be able to meet vertical and lateral stability for operating and installation conditions, 41 mm thick concrete coating is required. The greatest hydrodynamic force occurs in operating condition of 165.693 N/m based on DNVGL-RP-F109 and 154.150 N/m based on finite element. The difference of those result is only 6.96%.
Kehandalan Struktur Anjungan Lepas Pantai Terpancang Empat Kaki di Perairan Natuna Hermanto, Mochammad Fathurridho; Nandalianadhira, Nafisa
Rekayasa Vol 15, No 3: Desember 2022
Publisher : Universitas Trunojoyo Madura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21107/rekayasa.v15i3.16663

Abstract

The design of offshore platforms in Indonesia generally uses Working Stress Design (WSD) method rather than Load and Resistance Factor Design (LRFD) method. Whereas the LRFD method produces designs that better describe real conditions with load and capacity factors. The load and capacity factors are obtained from consideration of the uncertainty or randomness of their values. One of the load factors used is the environmental load factor. The environmental load factor of LRFD method is obtained based on environmental characteristics not in Indonesian waters. There are differences in the environmental characteristics of each water. Uncertainty of environmental loads in the offshore platforms design is wave height, current velocities, and wind speed. To get a structure designed according to the characteristics of the waters in Indonesia, an environmental load factor is needed in accordance with the characteristics of Indonesian water. To achieve that, structural reliability analysis is needed. Structures reliabilty represents the possibility of the structure's performance criteria being met which is expressed by the reliability index. The reliability index of structures designed using the WSD method used as a reference for LRFD method. In this study, reliability analysis was carried out using the reserve strength ratio value from the pushover analysis on WSD method. The reliability index of the structure model is 4.10. This value is categorized as high reliability. This results can be used as a reference to determine the environmental load factor of Indonesian water in the future.
Fatigue Sensitivity Analysis of Offshore Fixed Platform Structure in The Natuna Sea Nafisa Nandalianadhira; Mochammad Fathurridho Hermanto; Aqsha Khaylla Riquelle; Andreas Owen Hotman Nainggolan
Rekayasa Vol 19, No 1: January - April 2026
Publisher : Universitas Trunodjoyo Madura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21107/rekayasa.v19i1.30551

Abstract

Offshore fixed platform is one of the various types of platforms that are very suitable to be built in water areas with not too deep depths such as the Natuna Sea Waters area. This study analyzes fatigue in an offshore fixed platform in the Natuna Sea (309 ft depth), a region suitable for such structures due to its relatively shallow waters. The platform, with its tubular joints, is susceptible to fatigue from cyclical wave loads, particularly in the braces. The research employed in-place and fatigue analyses, using a deterministic method and adhering to API RP 2A-LRFD standards. In-place analysis revealed peak unity check values of 0.95 for the Pile (P1C) during operation and 0.96 for the Conductor (CO3) during storms. Maximum deflections were recorded: 14.728 inches horizontally at joint H005, and -3.339 inches vertically at joint C064. Fatigue analysis indicated a minimum service life of 73.40 years at joint 303L, located in the splash zone, where wave influence remains significant. Sensitivity analysis highlighted the crucial role of brace gap and chord thickness in determining service life. Increased brace gap negatively impacts service life, while chord thickness significantly influences it. This research provides critical insights for ensuring the structural integrity and longevity of offshore fixed platforms in similar environments.
Co-Authors Andreas Owen Hotman Nainggolan Apriliyani, Ulan Aqsha Khaylla Riquelle Elsa Rizkiya Kencana Gelfi, Mustarakh Hutajulu, Iin Debora Hutama, Surya Tri Esthi Wira Khaldun, Muhammad Hafidz Ibnu Maria Yosephine Simbolon Mochammad Fathurridho Hermanto Muhammad Mahendra Poetra Praja Muhammad Rizki Saleh Mustofa, Asep Nurul Ajiid Nalendra Jagat Lumintang Panggabean, Yehezkiel Pardede, Ida Juliana Puspita, Eka Suci Rifqi Asy'ari Samuel Samuel Santi Frestiqauli Sari, Shila Atika Satriyo Panalaran Setiono, Fadlillah Ihsan Shila Atika Sari Silalahi, Agnes Tresia Sitorus, Bintang Natan Wulandari, Eka Suci Puspita