The Experts below are selected from a list of 96 Experts worldwide ranked by ideXlab platform
Ivo Senjanović - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Analysis of Structural Details of an Oceangoing LPG Ship
Key Engineering Materials, 2007Co-Authors: Smiljko Rudan, Stipe Tomašević, Ivo SenjanovićAbstract:Structural details of ship structures are prone to fatigue damage mainly due to high-cycle wave load and low-cycle cargo loading/unloading. Full stochastic fatigue analysis of selected structural details on an oceangoing 6500 cbm LPG ship is presented. A critical Y-joint of Longitudinal Bulkhead and bilobe tank shell as well as double-bottom girder details are selected due to different reasons. The eccentricity of the Y-joint, leads to significant stress concentration. Saddle supports of gas tanks cause stress concentration in ship double bottom due to weight and dynamic loads. Wave load on ship structure is calculated using linear strip theory for ship in ballast condition and full ship. Wave load is transferred to ship finite element model and notch structural stresses are determined using finite element analysis. Stochastic fatigue analysis is then performed, taking into account sailing route and other ship operational parameters. Finally, fatigue damage summation is done and results are discussed.
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Structure design of cargo tanks in liquefied gas carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Vedran Slapničar, Zoran Mravak, Ana-maria LjuštinaAbstract:Different types of cargo tanks for gas sea-transport by Liquefied Gas Carriers are described. Design of bilobe tanks, as a complex task, according to the Classification Rules and the USCG Requirements is analysed. This includes selection of special material for high pressure and low temperature, determination of internal pressure consisting of design vapour pressure and liquid pressure that depends on ship motion in rough sea. Furthermore, it includes calculation of tank scant-lings, i.e. shell thickness, and design of Longitudinal Bulkhead, swash Bulkhead, vacuum rings and stiffening rings. Stabil-ity of cylindrical shells and torispherical dished ends is considered. Special attention is paid to the FEM analysis of the stiffening rings. The design procedure is illustrated in case of an LPG Carrier with one ordinary cylindrical tank and huge bilobe tank. Some comments are given how to improve tank design for production.
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Reinforcement of Imperfect Bilobe Cargo Tanks in Liquefied Gas Carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
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Remedy for misalignment of bilobe cargo tanks in liquefied Petroleum Gas Carriers
Journal of ship production, 2004Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
Smiljko Rudan - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Analysis of Structural Details of an Oceangoing LPG Ship
Key Engineering Materials, 2007Co-Authors: Smiljko Rudan, Stipe Tomašević, Ivo SenjanovićAbstract:Structural details of ship structures are prone to fatigue damage mainly due to high-cycle wave load and low-cycle cargo loading/unloading. Full stochastic fatigue analysis of selected structural details on an oceangoing 6500 cbm LPG ship is presented. A critical Y-joint of Longitudinal Bulkhead and bilobe tank shell as well as double-bottom girder details are selected due to different reasons. The eccentricity of the Y-joint, leads to significant stress concentration. Saddle supports of gas tanks cause stress concentration in ship double bottom due to weight and dynamic loads. Wave load on ship structure is calculated using linear strip theory for ship in ballast condition and full ship. Wave load is transferred to ship finite element model and notch structural stresses are determined using finite element analysis. Stochastic fatigue analysis is then performed, taking into account sailing route and other ship operational parameters. Finally, fatigue damage summation is done and results are discussed.
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Sigurnost konstrukcije spremnika na brodovima za prijevoz ukapljenog plina
2006Co-Authors: Smiljko RudanAbstract:Liquefied gas is one of the most important sources of energy nowadays. Worldwide it is being transported by pipelines or in liquefied state in tanks on Liquefied Natural Gas or Liquefied Petroleum Gas carriers. The independent tanks of type C, which contain liquefied gas both under pressure and refrigerated, are most commonly made in cylindrical or bilobe shape and are designed according to the Rules of classification societies. Absence of any serious incidents in seagoing transport is good evidence of the reliability of these rules and the tank construction itself. However, simple rules may not provide insight into actual behavior of ship and tank construction nor do they provide answer to the specific practical questions arising from the tank design and assembly practice. At the same time the tanks are becoming larger and therefore their constructions is becoming more technologically demanding, the fixed sailing routes are being replaced by the worldwide charter sailing, efforts are made to assure safe transport in the case of partially filled tanks or tanks under higher pressure. These reasons give rise to the need for more accurate analysis and better understanding of ship structure behavior subjected to realistic hydrodynamic loading. At the same time, shipbuilding practice requires answers to open problems of tank structure reliability, particularly related to stress concentration in thin shell structures, imperfection of geometry due to technical and other limitations during the tank assembly process, fatigue strength assessment of critical tank structural details, etc. This thesis presents both analytical and numerical methods for direct calculation of LPG tank structure safety. An overview of the theory of thin shells of revolution is presented and approximate analytical expressions for forces and deformations determination are given for cylindrical, conical, spherical and toroidal shells. A full spectral analysis is described in detail for each of its four steps: the hydrodynamic load calculation, quasi-static analysis of ship structure response, evaluation of notch stress transfer functions at the weld toe, statistical analysis and longterm distribution of notch stress as function of ship sailing condition and the calculation of highcycle fatigue damage for the structural detail under observation. The application of the method is presented through illustrative example: full parametric spectral analysis of imperfect Y-joint of cylindrical shells and Longitudinal Bulkhead of a bilobe tank in 6500 m3 LPG carrier. Different values of Y-joint eccentricity are found and measured on the existing bilobe tank, leading to high stress concentration and the presence of bending moment in membrane theory designed structure. Therefore, a comprehensive analytical and numerical analysis of Y-joint is performed and remedies for this imperfection are proposed in a systematic manner. Furthermore, low-cycle fatigue analysis methods are presented since low-cycle fatigue governs a significant part of the fatigue life of structural details subjected to tank pressure variation during cargo loading and unloading cycles. The application of the method is illustrated by low-cycle fatigue damage estimation for different values of Y-joint eccentricity. Finally, cumulative high-cycle and lowcycle fatigue damage concepts are presented. The stress concentration has been analyzed both by analytical and numerical methods in the case of cylindrical and hemispherical shells and in the case of imperfect joint of tank dish shells where a small angle conical joint had been formed. In the end, the scientific contribution of the performed research has been pointed out as well as the verification of research results through their practical application in shipbuilding practice.
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Structure design of cargo tanks in liquefied gas carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Vedran Slapničar, Zoran Mravak, Ana-maria LjuštinaAbstract:Different types of cargo tanks for gas sea-transport by Liquefied Gas Carriers are described. Design of bilobe tanks, as a complex task, according to the Classification Rules and the USCG Requirements is analysed. This includes selection of special material for high pressure and low temperature, determination of internal pressure consisting of design vapour pressure and liquid pressure that depends on ship motion in rough sea. Furthermore, it includes calculation of tank scant-lings, i.e. shell thickness, and design of Longitudinal Bulkhead, swash Bulkhead, vacuum rings and stiffening rings. Stabil-ity of cylindrical shells and torispherical dished ends is considered. Special attention is paid to the FEM analysis of the stiffening rings. The design procedure is illustrated in case of an LPG Carrier with one ordinary cylindrical tank and huge bilobe tank. Some comments are given how to improve tank design for production.
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Reinforcement of Imperfect Bilobe Cargo Tanks in Liquefied Gas Carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
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Remedy for misalignment of bilobe cargo tanks in liquefied Petroleum Gas Carriers
Journal of ship production, 2004Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
Ana-maria Ljuština - One of the best experts on this subject based on the ideXlab platform.
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Structure design of cargo tanks in liquefied gas carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Vedran Slapničar, Zoran Mravak, Ana-maria LjuštinaAbstract:Different types of cargo tanks for gas sea-transport by Liquefied Gas Carriers are described. Design of bilobe tanks, as a complex task, according to the Classification Rules and the USCG Requirements is analysed. This includes selection of special material for high pressure and low temperature, determination of internal pressure consisting of design vapour pressure and liquid pressure that depends on ship motion in rough sea. Furthermore, it includes calculation of tank scant-lings, i.e. shell thickness, and design of Longitudinal Bulkhead, swash Bulkhead, vacuum rings and stiffening rings. Stabil-ity of cylindrical shells and torispherical dished ends is considered. Special attention is paid to the FEM analysis of the stiffening rings. The design procedure is illustrated in case of an LPG Carrier with one ordinary cylindrical tank and huge bilobe tank. Some comments are given how to improve tank design for production.
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Reinforcement of Imperfect Bilobe Cargo Tanks in Liquefied Gas Carriers
2005Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
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Remedy for misalignment of bilobe cargo tanks in liquefied Petroleum Gas Carriers
Journal of ship production, 2004Co-Authors: Ivo Senjanović, Smiljko Rudan, Ana-maria LjuštinaAbstract:Short review of Liquefied Gas Carriers, i.e. Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) Carriers, is given. In general for gas transport integral tanks, membrane tanks, semi-membrane tanks and independent tanks are used depending on design features. The independent tanks of different shapes, which are further subdivided into A, B and C type related to design pressure, are described. Special attention is paid to remedy of misalignment in a 3000 m3 bilobe cargo tank of a 8350 m3 LPG Carrier as a result of manufacturing difficulties. Namely, some eccentricity in the Y-joint of tank shells and Longitudinal Bulkhead usually remain during fabrication that causes additional stress concentration. First, this problem is considered theoretically, and then numerically by FEM as a 2D task. Complete and reliable solution is achieved by a 3D FEM analysis of a tank segment between two vacuum rings. Necessary reinforcement of the Y-joint by set of knees and bars, depending on value of shells eccentricity, is recommended in order to reduce stress level below the allowable value. The obtained results are presented in a practical diagram for general use. Following given instructions cargo tanks of the considered LPG are reinforced and submitted to the hydraulic test with water pressure 50% higher of the design pressure. Passing this test successfully the approval of the relevant Classification Society is obtained.
Radoslav Pavazza - One of the best experts on this subject based on the ideXlab platform.
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On the cross-section distortion of large tankers subjected to bending
2006Co-Authors: Radoslav Pavazza, Branko Blagojević, Bože PlazibatAbstract:The paper deals with distortion of hull cross-sections of large modern tankers with one Longitudinal Bulkhead subjected to bending in the vertical plane of symmetry. The cross-section distortion is considered in the limit case. It is assumed that hull panels — bottom, deck, sides and Longitudinal Bulkheads — are hinged along their Longitudinal edges. The additional stresses and displacements due to distortion with respect to the stresses and displacements of the ordinary hull girder bending theory are analysed. The assumption of “ hinged cross-sections” is opposite to the assumption of “ rigid cross-sections” . Both are limiting cases of stresses and deformations of actual hull structures, particularly in the case of large tankers. A comparison with the results of the finite element analysis is provided.
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On the effective breadth problem of deck plating of ships with Longitudinal Bulkheads
International shipbuilding progress, 2001Co-Authors: Radoslav Pavazza, Bože Plazibat, Ado MatokovićAbstract:An approximate analytical method of estimating effective breadth of deck plating is presented. The deck plating in the region of 0.4L amidships is considered, as subjected to linearly distributed line loads along the edges of the deck plating and in way of the Longitudinal Bulkheads, together with Longitudinal normal forces at the ends of 0.4 L region. It is assumed that the contraction of the deck plating is small (not neglected). Analytical solutions are obtained for the stress distribution in the deck plating of ships without Longitudinal Bulkheads, for ships with a central Longitudinal Bulkhead and also for two symmetrically located Longitudinal Bulkheads. The method is applicable for ships without cargo hatch openings only, as tankers. The results are checked by the finite element method.
Bože Plazibat - One of the best experts on this subject based on the ideXlab platform.
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On the cross-section distortion of large tankers subjected to bending
2006Co-Authors: Radoslav Pavazza, Branko Blagojević, Bože PlazibatAbstract:The paper deals with distortion of hull cross-sections of large modern tankers with one Longitudinal Bulkhead subjected to bending in the vertical plane of symmetry. The cross-section distortion is considered in the limit case. It is assumed that hull panels — bottom, deck, sides and Longitudinal Bulkheads — are hinged along their Longitudinal edges. The additional stresses and displacements due to distortion with respect to the stresses and displacements of the ordinary hull girder bending theory are analysed. The assumption of “ hinged cross-sections” is opposite to the assumption of “ rigid cross-sections” . Both are limiting cases of stresses and deformations of actual hull structures, particularly in the case of large tankers. A comparison with the results of the finite element analysis is provided.
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On the effective breadth problem of deck plating of ships with Longitudinal Bulkheads
International shipbuilding progress, 2001Co-Authors: Radoslav Pavazza, Bože Plazibat, Ado MatokovićAbstract:An approximate analytical method of estimating effective breadth of deck plating is presented. The deck plating in the region of 0.4L amidships is considered, as subjected to linearly distributed line loads along the edges of the deck plating and in way of the Longitudinal Bulkheads, together with Longitudinal normal forces at the ends of 0.4 L region. It is assumed that the contraction of the deck plating is small (not neglected). Analytical solutions are obtained for the stress distribution in the deck plating of ships without Longitudinal Bulkheads, for ships with a central Longitudinal Bulkhead and also for two symmetrically located Longitudinal Bulkheads. The method is applicable for ships without cargo hatch openings only, as tankers. The results are checked by the finite element method.
