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Nafisa Nandalianadhira
Institut Teknologi Sumatera
Agriculture, Biological Sciences & Forestry Computer Science & IT Electrical & Electronics Engineering Engineering Physics

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Kehandalan Struktur Anjungan Lepas Pantai Terpancang Empat Kaki di Perairan Natuna Mochammad Fathurridho Hermanto; Nafisa Nandalianadhira
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.
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%.
Co-Authors Mochammad Fathurridho Hermanto