Studi Eksperimen Respon Gerak Dinamis Floating Crane Barge Saat Operasi Pengangkatan Struktur Dalam Laut Bergelombang

Firdaus, Nurman (2021) Studi Eksperimen Respon Gerak Dinamis Floating Crane Barge Saat Operasi Pengangkatan Struktur Dalam Laut Bergelombang. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Pemanfaatan floating crane barge semakin meningkat dengan adanya banyak permintaan aktivitas instalasi dan deccommisioning modul struktur lepas pantai. Gerakan crane barge dalam kondisi lingkungan bergelombang menimbulkan gerakan struktur terangkat yang terhubung oleh tali pengangkat di crane tip. Respon dinamis pada tali yang diinduksi oleh gerakan dinamis struktur terangkat mempengaruhi kembali pada respon gerak floating crane barge. Kondisi tinggi gelombang yang kecil dapat berkontribusi secara signifikan menimbulkan gaya hidrodinamika dan gaya/momen eksternal selama operasi pengangkatan. Gerakan struktur terangkat yang disebabkan respon gerak crane barge berlebih menimbulkan amplitudo besar. Sehingga, kriteria batas kondisi gelombang yang aman menjadi faktor penting dalam operasi crane barge. Selain itu, prediksi gerak kopel secara akurat pada operasi pengangkatan tidak mudah dilakukan pada sistem beban pengangkatan. Permasalahan ini yang mendorong penelitian Tesis untuk mengetahui respon gerak kopel pada floating crane barge dan struktur terangkat. Interaksi dinamis gerak kopel pada sistem multibody operasi pengangkatan dilakukan berdasarkan simulasi eksperimen laboratorium dengan rasio skala model 1:28. Model floating crane barge dilengkapi dengan struktur crane dan sistem tambat. Struktur terangkat disederhanakan berbentuk persegi yang memiliki massa sekitar 4 % dari massa floating crane barge. Untuk mengetahui pengaruh muatan struktur terangkat, kondisi eksperimen dilakukan variasi load case tanpa muatan, dan muatan dengan sudut putar struktur crane 0o, 45o dan 90o. Respon gerak kopel dalam simulasi eksperimen dievaluasi dengan variasi kondisi gelombang arah beam sea. Berdasarkan hasil eksperimen, interaksi gerak kopel terlihat dengan jelas adanya fenomena resonansi frekuensi pada kedua spektra respon gerak floating crane barge dan struktur terangkat. Pada struktur crane dengan sudut putar 0o, gerakan roll pada floating crane barge menunjukkan load case dengan muatan lebih kecil dibanding load case tanpa muatan untuk kondisi gelombang yang relatif lebih besar. Gerakan roll pada struktur crane dengan sudut putar 90o mengalami kenaikan respon secara signifikan sebesar 150% saat periode gelombang mendekati frekuensi alami gerakan vertikal struktur terangkat. Batasan aman operasi pengangkatan dengan floating crane barge dilakukan pada struktur crane dengan sudut putar 0o dalam kondisi parameter gelombang kode variasi IRREG2. Karakteristik RAO hasil eksperimen sesuai dengan model linier yang dilakukan dengan penyelesaian persamaan gerak kopel multibody 9 derajat kebebasan berbasis metode ranah frekuensi (frequency-domain). ================================================================================================= The utilization of floating crane barge is increasing with the demand for installation and decommissioning activities of offshore structure module. The motions of a crane barge in sea wave condition cause the movements of a lifted structure which is connected by the hoisting rope on the crane tip. The dynamic response of the rope induced by the dynamic movement of a lifted structure affects the motion response of a floating crane barge again. The condition of small wave height can significantly contribute to generate the hydrodynamic forces and the external forces/moments during a lifting operation. The movements of a lifted structure caused by an excessive motion response of a crane barge raise a large amplitude. Thus, the safely limited criteria of wave conditions are an important factor in crane barge operations. In addition, the accurate prediction of coupled motion in a lifting operation is not an easy to do on the lifting load system. This problem prompted the Thesis research to study the coupled motion response on the floating crane barge and the lifted structure. The dynamic interaction of coupled motion for multibody system of a lifting operation was carried out based on the simulation of laboratory experiment with a model scale ratio of 1:28. The model test of floating crane barge is equipped with a crane structure and a mooring system. The lifted structure is simplified to a square shape which has the weight of about 4 % of the weight of the floating crane barge. In order to investigate the effect of a lifted structure load, the experimental conditions were conducted variations in load cases of without and with a suspended load in rotating angles of a crane structure of 0 deg, 45 deg and 90 deg. The coupled motion responses in the experimental simulation were evaluated by varying the wave conditions with heading beam sea. Based on the experimental results, the interaction of coupled motion clearly showed the phenomena of frequency resonance in both the motion response spectra of a floating crane barge and a lifted structure. On a crane structure with a rotating angle of 0 deg, the roll motion of floating crane barge presented a load case of with a suspended load smaller than a load case of without at a relatively larger wave condition. The roll motion of the crane structure with a rotating angle of 90 deg experienced a significantly increased response about 150 % when the wave period was close to the natural frequency of vertical movement of a lifted structure. The safe limitation of lifting operation by a floating crane barge is carried out on the crane structure with a rotating angle of 0 deg under wave condition of variation code IRREG2. The RAO characteristics of the experimental results were a good agreement with the linear model by solving the multibody coupling equation of 9 degrees of freedom based on the frequency domain method.

Item Type: Thesis (Masters)
Uncontrolled Keywords: eksperimen, floating crane barge, gelombang, gerak kopel, model linier experiment, floating crane barge, waves, coupled motion, linear model
Subjects: Q Science > Q Science (General) > Q180.55.M38 Mathematical models
T Technology > TC Hydraulic engineering. Ocean engineering
V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering
Divisions: Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38101-(S2) Master Thesis
Depositing User: Nurman Firdaus
Date Deposited: 20 Aug 2021 03:35
Last Modified: 20 Aug 2021 03:35
URI: https://repository.its.ac.id/id/eprint/88796

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