ANALISIS FATIGUE PADA KONSTRUKSI CRANE PEDESTAL FLOATING STORAGE AND OFFLOADING (FSO) ARCO ARDJUNA PERTAMINA HULU ENERGI,ONWJ

HAMZAH, MOCH. (2016) ANALISIS FATIGUE PADA KONSTRUKSI CRANE PEDESTAL FLOATING STORAGE AND OFFLOADING (FSO) ARCO ARDJUNA PERTAMINA HULU ENERGI,ONWJ. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Dalam tugas akhir ini dilakukan analisis umur kelelahan konstruksi bow crane pedestal yang akan dipasang di atas konstruksi midship section nomer 18 FSO Arco Ardjuna PHE, ONWJ yang tertambat pada sebuah sistem tambatan Single Point Mooring (SPM). Analisis ini dilakukan sebagai dasar acuan perancangan, inspeksi dan reassessment crane pedestal sebagai konstruksi penyangga struktur crane yang akan dipasang dan beroperasi diatasnya. Dengan mengetahui perilaku gerak FSO Arco Ardjuna yang tertambat pada Single Point Mooring akibat beban lingkungan perairan operasi FSO Arco Ardjuna, maka dapat dihitung berapa besar beban akibat gaya translasi dan momen gaya (torsi) yang terjadi pada crane akibat akselerasi struktur FSO dalam kondisi tertambat pada SPM. Selain itu, dianalisis pula berapa besar shear stress dan total bending moment pada setiap konstruksi midship section dengan perhitungan kekuatan memanjang akibat beban perairan dalam kondisi still water, calm water, dan akibat gelombang sagging maupun hogging. Di dalam analisis ini beban momen angin juga dihitung berdasarkan bentuk area penampang angin pada crane pedestal. Kombinasi dari keseluruhaan beban – beban tersebut termasuk berat struktur sendiri adalah inputan dalam analisis tegangan untuk mendapatkan Hot-Spot Stress yang akan dijadikan dasar perhitungan umur kelelahan konstruksi crane pedestal menggunakan metode S-N Curve berdasarkan hukum kegagalan Palmgren Miner dengan mengestimasi kegagalan akibat kelelahan dengan simplified method. Dari hasil pemodelan numerik yang dilakukan, diketahui bahwa perilaku gerak terbesar pada FSO Arco Ardjuna dalam kondisi tertambat yaitu sebesar 1,2 0/m untuk gerakan roll saat kondisi muatan kosong. Untuk beban torsi crane terbesar terjadi akibat akselerasi gerakan roll sebesar 2051,7 kN.m serta shear force dan bending moment pada frame 16 terbesar terjadi akibat efek hogging masing – masing sebesar 48,74 ton dan 38,63 ton.m. Berdasarkan hasil analisis tegangan yang telah dilakukan nilai tegangan terbesar yang terjadi pada konstruksi bow crane pedestal adalah 129,88 Mpa dengan nilai deformasi sebesar 0,75 mm. Hasil tersebut masih diijinkan apabila mengacu pada tegangan ijin dan nilai deformasi yang dianjurkan ABS yaitu 225 MPa dan 11,2 mm. Berdasarkan tegangan maksimum tersebut, diperoleh hasil perhitungan umur kelelahan konstruksi bow crane pedestal sebesar 115,8 tahun. =================================================================================================== In this paper, the bow crane pedestal construction that will be installed on top of No.18 midship section of FSO Arco Ardjuna Pertamina Hulu Energi ONWJ that moored to single point mooring structure will be analyzed in fatigue life analysis to obtained its operationservice life. This analysis must be done, because it is important to predict how long the service life of a structure or construction design before the installation or as the references for inspection and reassessment. By doing global motion analysis of FSO while its moored to SPM, so the motion acceleration of FSO that cause the translation force and torque of crane structure can be obtained. Furthermore, because of the crane pedestal will be modelled with a few of midship section (No.16,17,18,19 and 20), So the shear stress and total bending moment of each section will be considered and analyzed using longitudinal strength analysis due to effect of still water, calm water and sagging-hogging waves. In this fatigue life analysis the moment caused by wind force will be considered too, by considering the crane pedestal elevation and its shape factor. All of these kind of loading which give effects to crane pedestal construction will be combined in stress analysis to obtain the Hot-Spot Stress that will use in fatigue life analysis using S-N Curve based on Palmgren Miner’s Failure Law to estimate damage caused by fatigue with simplified method. Based on the numerical analysis that has been done, obtained the largest magnitude motion of FSO in moored condition is 1,2 0/m for the roll motion. The largest magnitude of crane torque impact to crane pedestal construction due to FSO motion acceleration is 2051,7 kN.m caused by roll motion and the largest number of shear force and bending moment at No. 16 midship section are 48,74 tonne and 38,63 tonne.m. Due to all of the loading and its combination, the largest number of stress and deformation that ever occured in stress analysis of this fatigue analysis is 129,88 MPa with 0,75 mm of deformation. That number of stress and deformation are still allowed by refer The American Bureau of Ship Rules of maximum allowable stress and deformation that recommend the number of stress and deformation must be below of 225MPa and 11,2 mm of deformation. Based on that maximum occured stress, obtained the fatigue life of bow crane pedestal of FSO Arco Ardjuna is 115,8 years.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: FSO, bow crane pedestal, maximum principal stress, hot-spot stress, simplified fatigue assessment
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering
Divisions: Faculty of Marine Technology > Ocean Engineering > (S1) Undergraduate Theses
Depositing User: Mr. Fandika aqsa
Date Deposited: 11 Jan 2017 07:12
Last Modified: 26 Dec 2018 08:29
URI: http://repository.its.ac.id/id/eprint/1486

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