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"This book provides a brief overview of passive, semi-active and active control schemes to deal with vibration of offshore platforms. It then comprehensively and systematically discusses the recent advances in active systems with optimal, sliding model, delayed feedback and network-based control. Intended for readers interested in vibration control and ocean engineering, it is particularly useful for researchers, engineers, and graduate students in the fields of system and control community, vibration control, ocean engineering, as well as electrical and electronic engineering."

"ABSTRAKProduksi minyak dan gas di Indonesia telah dilakukan lebih dari tiga puluhtahun, lebih dari 70% anjungan lepas pantai di Indonesia telah malampaui umurdesainnya dan akan terus meningkat jumlahnya seiring berjalannya waktu sertabiaya dekomisionig dan membangun platform baru yang relatif mahal. Platformyang mengalami penuaan dan penurunan akibat korosi, kerusakan dan anomalilainnya akan memunculkan masalah terhadap integritas struktur kecuali dikeloladan dirawat dengan baik dengan program inspeksi, perawatan, perbaikan sertametode analisis struktural yang baik. Program inspeksi bawah air rutin telah diaturpemerintah dalam keputusan Ditjen Migas No. 21.K/38/DJM/1999, dan sejaktahun 2013 pemerintah telah mengeluarkan persetujuan penerapan rencanainspeksi bawah air berbasis risiko dalam surat edaran Ditjen Migas no8433/18.01/DMT/2013 yang memberikan kesempatan kepada operator untukmengoptimalkan sumber daya untuk program peningkatan integritas struktural.Salah satu faktor yang menentukan risiko suatu platform adalah kemungkinankegagalan yang selama ini dinilai dengan pendekatan semikuantitatif. Tulisan iniakan membahas pendekatan kuantitatif terhadap penilaian kemungkinankegagalan anjungan lepas pantai berdasarkan tingkat robustness melalui analisakekuatan ultimit yang akan meningkatkan konfidensi dalam penilaiankemungkinan kegagalan sesuai dengan karakter struktur, metocean, serta anomaliplatform di wilayah perairan Indonesia. Hasil penelitian menunjukkan bahwametode semikuantitatif yang selama ini diterapkan dalam perencanaan inspeksiberbasis risiko untuk menyusun kemungkinan kegagalan platform telah cukupmengidentifikasi sejumlah faktor yang berpotensi memperngaruhi kemunduranstruktur, namun tidak cukup memberikan gambaran pengaruhnya terhadap tingkatkemunduran platform. Pendekatan kuantitaif dapat memberikan gambaranpengaruh anomali terhadap kemunduran platform yang lebih baik.

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ABSTRACTProduction of oil and gas in Indonesia has been performed over thirtyyears, more than 70% of offshore platforms in Indonesia has exceed of design lifeand will continue increase in number over time since decommisioning cost andbuild a new platform is relatively expensive. Agein and deteriorated offshoreplatforms as a result of corrosion, damage and other anomalies would bring up theissue of the structural integrity unless managed by inspection, maintenance, repairprogram and good structural analysis methods. Routine underwater inspectionprogram has been regulated by the government on Keputusan Ditjen Migas No.21.K/3/DJM/1999, since 2013 the government has issued approval of theimplementation risk-based underwater inspection planning on Surat Edaran DitjenMigas No. 8433/18.01/DMT/2013, which provides the opportunity for theoperator to optimize the resources to improve the structural integrity. One of thefactor that determine the risk of an offshore platform is the Likelihood of Failure(LoF) that assessed by semiquantitative approach. This paper will discuss thequantitative approach as a tools to assess the Likelihood of Failure of offshoreplatforms based on the level of robustness through ultimate strength analysis thatwill increase confidence to assess the Likeihood of Failure in accordance with thecharacter of the structure, metocean, as well as anomalies of offshore platforms inthe territorial waters of Indonesia. Result shown that the recent semiquantitativeapproach to identifiy likelihood of failure is enough to capture some potentialfactor affecting platform deterioration, however can not present level of platformdeterioration for each factor. Quantitative approach give better acknowledge aboutthe effect of anomaly to platform deterioration."

"ABSTRAKPlatform Jacket yang telah difabrikasi di darat akan dibawa/ ditransportasi ke site dengan menggunakan kapal tongkang (barge) untuk di-install di lapangan migas. Selama proses transportasi diperlukan suatu pengikatan struktur jacket ke deck barge agar struktur Jacket tetap stabil diatas barge. Sistem pengikatan yang disebut seafastening ini harus di desain kuat untuk menerima beban yang diakibatkan oleh pergerakan (motion) kapal, yakni tiga gerakan translasional (surge, sway, heave) dan tiga gerakan rotasional (pitch, roll dan yawn). Gerakangerakan ini menimbulkan percepatan pada barge yang berakibat timbulnya gaya tambahan pada struktur diatasnya dan hal ini mempengaruhi tegangan pada seafastening. Perangkat lunak Multi Operational Structural Computer System (MOSES) dipergunakan sebagai alat bantu untuk permodelan Barge dan Jacket, serta perhitungan karakteristik Response Amplitude Operator (RAO) yang diakibatkan oleh beban lingkungan.Selanjutnya untuk menghitung tegangan yang terjadi pada seafastening, digunakan perangkat lunak Structural Analysis Computer System (SACS) dengan pembebanan berupa beban mati, beban angin dan beban inersia yang diakibatkan oleh motion kapal tongkang/ Barge. Besarnya tegangan harus memenuhi kriteria Unity Check (UC).

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ABSTRACT

Platform Jacket which fabricated in yard will be transported to the site with barge for installation. During the transport process, strong fastening system from jacket to deck barge is required so that the Jacket Structure remains stable on Barge. Fastening system that called seafastening must be in strong designs to accept the load caused by the movement of the barge, three translational motion (surge, sway, heave) and three rotational movement (pitch, roll and yawn). These movements cause the acceleration of the barge which result in the emergence additional force on the structure above, and this influences the stress at seafastening. Multi Operational Structural Engineering Simulator (MOSES) software is used as a tool for modeling of Barge and Jacket, as well as the calculation of the characteristics Response Amplitude Operator (RAO) caused by environmental.

Furthermore, to calculate the stress that occurs in seafastening, software Structural Analysis Computer System (SACS) is used, with the loads on a construction during seafastening is dead load of the structure, wind load and innertia load caused by the motion of barge / Barge. The magnitude of the stress of seafastening must meet the criteria of Unity Check (UC)."

"Spun pile yang terdapat di Indonesia masih menggunakan tulangan transversal dengan rasio volumetrik yang jauh dibawah persyaratan SNI. Penggunaan steel jacket pada spun pile selain sebagai perkuatan untuk spun pile juga untuk memenuhi kebutuhan tulangan transversal pada spun pile tersebut. Penelitian ini akan mengamati pengaruh penggunaan steel jacket terhadap perilaku spun pile dalam menahan beban aksial dan lateral melalui pemodelan menggunakan perangkat lunak ABAQUS. Uji parametrik untuk mengetahui pengaruh steel jacket dan perilaku spun pile dilakukan dengan memberikan variasi beban aksial, material dan tebal steel jacket, serta lekatan antara steel jacket dengan spun pile. Analisis hasil uji parametrik diperoleh melalui pengamatan kapasitas dan daktilitas melalui kurva , rasio volumetrik tulangan transversal, tegangan, dan regangan. Penggunaan steel jacket baja mutu tinggi dan baja normal diketahui dapat meningkatkan kapasitas lentur spun pile, namun juga mengurangi daktilitas dari spun pile tersebut. Lekatan steel jacket pada spun pile yang lebih lemah menyebabkan steel jacket mengalami slip sehingga dapat mengurangi kapasitas lentur spun pile. Steel jacket mampu memenuhi kebutuhan tulangan transversal pada spun pile karena mampu meningkatkan rasio volumetrik tulangan transversal pada spun pile secara signifikan dan mampu mengurangi tegangan dan regangan maksimum yang bekerja pada tulangan spiral.

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Spun pile available in Indonesia still uses transverse reinforcement with volumetric ratio that is much lower that SNI requirement. Steel jacket usage on spun pile besides as spun pile strengthening is also to fulfill the requirements of transverse reinforcement. The purpose of this study is to observe the effects of steel jacket to spun pile behaviour to withstand axial and lateral loads by modeling with ABAQUS software. Parametric studies used to observe the effects was done by varying axial loads, steel jacket materials and thicknesses, and bonds between steel jacket and spun pile. Analysis for parametric studies was obtained from investigation of capacity and ductility from curve, transverse reinforcement volumetric ratio, stresses, and strains. It is known that high strength and normal strength steel jacket can increase bending capacity of the spun pile, but also decrease the spun pile’s ductility. Weaker bonds between steel jacket and spun pile can cause steel jacket to slip thereby reduces bending capacity of spun pile. Steel jacket can fulfill the requirements of spun pile transverse reinforcement for increasing transverse reinforcement volumetric ratio significantly and reducing maximum stresses and strains acting on the spiral reinforcement.

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"The fixed jacket isstill the most common offshore structure used for drilling and oil production.The structure consists of tubular members interconnected to form athree-dimensional space frame, which can be categorized into a columnstructure. The structure usually has four to eight legs that are battered toachieve stability against axial compressive loads and toppling due to waveloads. The configuration of a typical member on the jacket structure hassignificant influence on buckling and fatigue strength. Horizontal and diagonalbraces play an important role in resisting the axial compression and wave loadon the global structure. Thispaper discusses the effect of symmetrical and asymmetrical configuration shapesin buckling and fatigue strength analysis on two types of fixed jacket offshoreplatforms. The axial compressive and lateral (wave) loads were considered andapplied to both structures. The material and dimensions of the two structureswere assumed to be constant and homogenous. Crack extension and corrosion werenot considered. To assess the buckling and fatigue strength of thesestructures, due to the symmetrical and asymmetrical configuration shape, thefinite element method (FEM) was adopted. Buckling analysis was performed onthese structures by taking two-dimensional planes into consideration to obtainthe critical buckling load for the local plane; fatigue life analysis was thencalculated to produce the fatigue life of those structures. The result obtainedby FEM was compared with the analytical solution for the critical bucklingload. The stress-strain curve was also applied to show the difference betweensymmetrical and asymmetrical shapes. For fatigue life analysis, the procedureof the response amplitude operator was applied."

"The fixed jacket is still the most common offshore structure used for drilling and oil production. The structure consists of tubular members interconnected to form a three-dimensional space frame, which can be categorized into a column structure. The structure usually has four to eight legs that are battered to achieve stability against axial compressive loads and toppling due to wave loads. The configuration of a typical member on the jacket structure has significant influence on buckling and fatigue strength. Horizontal and diagonal braces play an important role in resisting the axial compression and wave load on the global structure. This paper discusses the effect of symmetrical and asymmetrical configuration shapes in buckling and fatigue strength analysis on two types of fixed jacket offshore platforms. The axial compressive and lateral (wave) loads were considered and applied to both structures. The material and dimensions of the two structures were assumed to be constant and homogenous. Crack extension and corrosion were not considered. To assess the buckling and fatigue strength of these structures, due to the symmetrical and asymmetrical configuration shape, the finite element method (FEM) was adopted. Buckling analysis was performed on these structures by taking two-dimensional planes into consideration to obtain the critical buckling load for the local plane; fatigue life analysis was then calculated to produce the fatigue life of those structures. The result obtained by FEM was compared with the analytical solution for the critical buckling load. The stress-strain curve was also applied to show the difference between symmetrical and asymmetrical shapes. For fatigue life analysis, the procedure of the response amplitude operator was applied."

"Studying about cable stayed bridge become trend in the last few years. Since the improvement of the material technology and the need of longer bridge so the cable stayed bridge become more important in the last few years.Since the span become longer, so the structure will become more flexible and external load such are traffic, wind, rain and earthquake become more significant to the structure. When the displacement of the deck will increase, it will make uncomforting for human. Many scientists and engineers try to make a control of cable stayed bridge, so that the response will become safety and good for human comfort also.In this study we try to simulate the model from experiment to the behavior of the cable stayed bridge itself. We also try to control the response of the structure. This control that we have done must be realistic and easy to use.In fact with computer simulation we can do such sophisticated control, but the main problem if it's not applicable the control that we use become useless, otherwise it will be dangerous also if we get a result in reality far from out simulation.So in this study we do simple control to cable stayed bridge, and do some test that could be realistic in the reality. The sag of the cable is big and it will make a non linear effect. We do some analysis of cable stayed bridge in ANSYS 5.5.3 and do control simulation in SIMULINK by catching the static non linear result from ANSYS 5.5.3.The simulation that we done here to see the effectives of the control in many cases. We can be sure that the control is good if we get a good solution with the control of the structure."

"Studi perkuatan sambungan spun pile terhadap pile cap menggunakan zincalume diusulkan sebagai persyaratan untuk memenuhi rasio confinement spun pile buatan Indonesia. Selain itu, perkuatan bertujuan untuk meningkatkan kekuatan, daktilitas, dan serapan energi gempa oleh spun pile. Oleh karena itu, dilakukan studi eksperimen pada spun pile dengan beton pengisi dan perkuatan steel jacket akibat pembebanan siklik dan dibandingkan dengan benda uji tanpa perkuatan. Dilakukan juga pushover analysis secara monotonik untuk mengamati proses terjadinya sendi plastis dan strain pada material. Terdapat dua benda uji eksperimen berupa spun pile berdiameter 450 mm dengan perkuatan steel jacket yang diberikan beton pengisi bertulang dan salah satu benda uji tanpa beton pengisi bertulang, serta satu benda uji referensi berupa spun pile tanpa perkuatan steel jacket. Hasil eksperimen menunjukan perkuatan steel jacket terbukti dapat meningkatkan kekuatan dan daktilitas benda uji, tetapi masih belum dapat meningkatkan serapan energi gempa. Pengaruh tulangan pada beton pengisi terbukti dapat meningkatkan kekuatan dan daktlitas pada spun pile dengan adanya perkuatan steel jacketing. Parameter penelitian yang diguanakan untuk membandingkan benda uji adalah daktilitas, energi disipasi dan input, degradasi kekuatan dan kekakuan, momen – rotasi, dan kurva histeretik akibat pembebanan siklik.

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The study of strengthed spun pile to pile cap connection using zincalume is proposed as a requirement to meet the confinement ratio of spun pile made in Indonesia. In addition, the reinforcement added aims to increase the strength, ductility, and earthquake energy absorbtion by spun pile. Therefore, an experimental study was conducted on the spun pile with reinforced concrete and steel jacket reinforcement due to cyclic loading and compared with the specimen without steel jacket reinforcement. A monotonic pushover analysis was also carried out to observe the process of plastic hinge and strain on the material. There are two experimental specimens in the form of a spun pile with a diameter of 450 mm with steel jacket reinforcement provided with reinforced concrete and one other specimen without reinforced concrete, and one reference test object in the form of a spun pile without steel jacket reinforcement. The experimental results show that steel jacket reinforcement is proven to increase the strength and ductility of the test object, but still cannot increase the absorption of earthquake energy. The effect of reinforcement on infill concrete is proven to increase the strength and ductility of the spun pile with the presence of steel jacketing reinforcement. The research parameters used to compare the specimens were ductility, energy dissipation and input, strength and stiffness degradation, moment-rotation, and hysteretic curve due to cyclic loading."