• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.825-831
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• 2007

The use of high-strength aluminum alloys for ship and offshore structure generally has many benefits compared to the structural steels. These materials are used widely in a variety of fields, especially in the hull and deck of high speed craft, box-girder of bridges, deck and side plates of offshore structure. The structural weight can be reduced using these aluminum structure, which can enable high speed The characteristics of stress-strain relationship of aluminum structure are fairly different from the steel one, because of the influence of Heat Affected Zone(HAZ) by the welding processing. The HAZ of aluminum is much wider than that of steel with its high heat conductivity. In this paper, the ultimate strength characteristics of aluminum stiffened panel subjected to axial loading, such as the relationship between extent of HAZ and the behavior of buckling/ultimate strength, are investigated through the Finite Element Analysis with varying its range.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.348-363
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• 2013

The use of I-Core sandwich panel has increased in cruise ship deck structure since it can provide similar bending strength with conventional stiffened plate while keeping lighter weight and lower web height. However, due to its thin plate thickness, i.e. about 4~6 mm at most, it is assembled by high power $CO_2$ laser welding to minimize the welding deformation. This research proposes a volumetric heat source model for T-joint of the I-Core sandwich panel and a method to use shell element model for a thermal elasto-plastic analysis to predict welding deformation. This paper, Part I, focuses on the heat source model. A circular cone type heat source model is newly suggested in heat transfer analysis to realize similar melting zone with that observed in experiment. An additional suggestion is made to consider negative defocus, which is commonly applied in T-joint laser welding since it can provide deeper penetration than zero defocus. The proposed heat source is also verified through 3D thermal elasto-plastic analysis to compare welding deformation with experimental results. A parametric study for different welding speeds, defocus values, and welding powers is performed to investigate the effect on the melting zone and welding deformation. In Part II, focuses on the proposed method to employ shell element model to predict welding deformation in thermal elasto-plastic analysis instead of solid element model.

• Earthquakes and Structures
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• v.19 no.5
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• pp.315-329
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• 2020

Through bolt connections in Concrete Filled Steel Tubes (CFSTs) has been proved to be good in terms of seismic performance and constructability. Stiffened extended end plate connection with full through type bolt helps to avoid field weld altogether, and hence to improve the quality of joints. An experimental study was conducted on the hysteretic performance of square interior beam-column connections using flat extended end plates with through bolt. The study focuses on the effect of the bond between the tie rod and the core concrete on the cyclic performance of the joint. The study also quantifies how much the interior joint is getting strengthened due to the confinement effect induced by bi-directional bolting, which is widely used in 3D moment resisting frames. For a better understanding of the mechanism and for the prediction of shear capacity of the panel zone, a mathematical model was generated. The various parameters included in the model are the influence of axial load, amount of prestress induced by bolt tightening, anchorage, and the concrete strut action. The study investigates the strength, stiffness, ductility, and energy dissipation characteristics. The results indicate that the seismic resistance is at par with American Institute of Steel Construction (AISC) seismic recommendations. The bidirectional bolting and bond effect have got remarkable influence on the performance of joints.

• Journal of the Korean Institute of Navigation
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• v.20 no.1
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• pp.47-58
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• 1996

The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The main portion of ship structure is usually composed of stiffened plates. In these structures, plate buckling is one of the most important design criteria and buckling load may usually be obtained as an eigenvalue solution of the governing equations for the plate. To use the high tensile steel plate effectively, its thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. When the panel elastic buckling is allowed, it is necessary to get precise understandings about the post-buckling behaviour of thin plates. It is well known that a thin flat plate undergoes secondary buckling after initial buckling took place and the deflection of the initial buckling mode was developed. From this point of view, this paper discusses the post-buckling behaviour of thin plates under thrust including the secondary buckling phenomenon. Series of elastic large deflection analyses were performed on rectangular plates with aspect ratio 3.6 using the analytical method and the FEM.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.254-261
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• 2004

Until now, there are different kinds of design and evaluation method criteria for ship hulls and ship strength based on allowable stress design using past experiences. But for many sinking accidents of large ships in operation, it has also a doubt about allowable stress design. It is recognized that structural plastic collapse caused by large external force is a main cause of that accidents. Therefore, there is the need for new design criteria based on ultimate limit state with a consideration about progressive collapse behavior as a safety assessment of ship hulls. Also many aluminum alloy ships is built for the purposes of lightweight of ship hulls, with that, a developing of criteria based on ultimate limit state should be made. In this study, the ultimate strength characteristics of aluminum ship hull are investigated by the ALPS/USAS program using already developed design formula for aluminum plate and stiffened panel.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.344-351
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• 2000

In the design of plate girder web panels, it is required to evaluate accurately the elastic buckling strength under pure shear, pure bending and combined bending and shear. Currently, elastic buckling coefficients of web panels stiffened by transverse intermediate stiffeners are determined by assuming conservatively that web panels are simply supported at the juncture between the flange and web. However, depending upon the geometry and the properties of the plate girder bridge, upper juncture between the flange and web can be assumed as fixed because concrete deck prevents the rotational displacement of upper flange. In the present study, a series of numerical analyses based on finite element modeling is carried out to investigate the effects of the concrete deck, and the resulting data are quantified in simple equations.

• Journal of Ocean Engineering and Technology
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• v.34 no.2
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• pp.97-109
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• 2020

In this study, ultimate strength characteristics of clamped sandwich panels with metal faces and an elastic isotropic core under combined in-plane compression and lateral pressure loads are investigated to verify the applicability of the ultimate strength design formula for ship structures. Alternative elastomer-cored steel sandwich panels are selected instead of the conventional bottom stiffened panels for a Suezmax-class tanker and then the ultimate strength characteristics of the selected sandwich panels are examined by using nonlinear finite element analysis. The change in the ultimate strength characteristics due to the change in the thickness of the face plate and core as well as the amplitude of lateral pressure are summarized and compared with the results obtained by using the ultimate strength design formula and nonlinear finite element analysis. The insights and conclusions developed in the present study will be useful for the design and development of applications for sandwich panels in double hull tanker structures.

• Journal of Ship and Ocean Technology
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• v.7 no.4
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• pp.41-49
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• 2003

Welding deformation reduces the accuracy of ship hull blocks and decreases productivity due to the need for correction work. Preparing an error-minimizing guide at the design stage will lead to higher quality as well as higher productivity. Therefore, developing a precise method to predict the weld deformation is an essential part of it. This paper proposes an efficient method for predicting the weld deformation of complicated structures based on the inherent strain theory combined with the finite element method. A simulation of a stiffened panel confirmed the applicability of this method to simple ship hull blocks.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.167-179
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• 1999

The thin web panels of plate girders often need to be reinforced with transverse stiffeners to increase the shear strength. Since early 1960s, extensive researches have been conducted on the ultimate shear strength of plate girder webs with transverse stiffeners. These results have been first adopted into AASHTO(1970) and British Standard(1983) Specifications for the determination of the ultimate shear strength of transversely stiffened web panels. Although the main purposes of reinforcing web panels with longitudinal stiffeners are to increase the buckling strength and to control the lateral deflections due to bending, it has been reported that the longitudinal stiffeners increase the shear strength. However lack of studies has kept the effects of the longitudinal stiffeners on the ultimate shear strength from the design of plate girder web panels. In the present study an experimental investigation is carried out in order to assess the increment of the ultimate shear strength of shear web panels due to the longitudinal stiffeners and the results are compared with the existing failure theories.

• Composites Research
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• v.16 no.6
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• pp.16-22
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• 2003

This paper studied the AE(acoustic emission) characteristics of the laminated composite structures. The composite stiffened panels under the compressive loading emitted various AE signals when they buckled or changed the buckling modes. In addition, the failure initiated and propagation generated a lot of complex signals. From the continuous signal generation. we identified when the failures initiated and whether they propagated or not. The single lap joint of laminated plates under tensional load also generated AE signals when bonding region failed. The first failure occurrence and its propagation are monitored by generated AE signals. The characteristics of AE signals used in this analysis are cumulative hits, hit distribution, peak frequency of generated AE waveform and amplitude of signals. The analysis of AE signals shows that continuous increment of cumulative hits can be regarded as damage propagation and three dominant peak frequencies can correspond to typical failure modes in the laminated composites.