• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.551-559
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• 2003

In steel frames, the analysis and design techniques are based on either idealized fixed or pinned connections. In this case, it has the advantage that the structural analysis and the design procedure were simplified, but there could be given different results of analysis between the real steel frame connections and the idealized fixed and pinned connection. This is because the real connections would be analyzed by semi-rigid, and have some transfer of moment and rotational constraint about the loads. In this study, structural analysis program with considered connections that have joint rigidity of fixed, pinned and semi-rigid, was developed. Then, the effects of joint rigidity on strength and displacement. in steel frames subjected to lateral forces and axial forces, were investigate, and the results were compared with those of the Midas Gen. w program.

• Journal of Welding and Joining
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• v.29 no.6
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• pp.40-44
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• 2011

Brazing of a stainless steel was described in this article. Brazing is a joining technology without melting a substrate and joining temperature is higher than $450^{\circ}C$. Brazing can be broadly applicable across industries. In particular, brazing of stainless steel is widely used in aircraft parts, car engines, heat exchangers, etc. due to its excellent strength, corrosion resistance and other suitable characteristics. Characteristics of the stainless steel depend on their classification like austenitic, ferritic and martensitic stainless steels. In addition, there are many processes in brazing and various parameters such as brazing heat source, filler metals, joint design, etc. Therefore, it is necessary to know basic knowledge about brazing to achieve good brazing joint. Accordingly, properties of stainless steel and design of brazing joint and related process were described in this article.

• Steel and Composite Structures
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• v.32 no.1
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• pp.141-156
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• 2019

This paper presents the flexural behaviour of stainless steel beam-to-tubular column joints with extended endplates subjected to static loading. Moment-rotation relationships were investigated numerically by using Abaqus software with geometric and material nonlinearity considered. The prediction of damages among components was achieved through ductile damage models, and the influence of initial geometric imperfections and residual stresses was evaluated in large fabricated stainless steel joints involving hollow columns and concrete-filled columns. Parametric analysis was subsequently conducted to assess critical factors that could affect the flexural performance significantly in terms of the initial stiffness and moment resistance. A comparison between codes of practice and numerical results was thereafter made, and design recommendations were proposed for further applications. Results suggest that the finite element model can predict the structural behaviour reasonably well with the component damage consistent with test outcomes. Initial geometric imperfections and residual stresses are shown to have little effect on the moment-rotation responses. A series of parameters that can influence the joint behaviour remarkably include the strain-hardening exponents, stainless steel strength, diameter of bolts, thickness of endplates, position of bolts, section of beams and columns. AS/NZS 2327 is more reliable to predict the joint performance regarding the initial stiffness and moment capacity compared to EN 1993-1-8.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.66-70
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• 1999

In order to investigate the quantitative behavior of galvanic corrosion in weld joints between stainless std이 and carbon steel, electrochemical polarization experiments were performed at pH4, pH7 and pH10 with boric acid concentration 4000ppm, and water temperature were selected as $35^{\circ}$C and $60^{\circ}$C. As the results, the galvanic corrosion phenomena of carbon steel weld material at $60^{\circ}$C was revealed $2{1\over2}$ times higher corrosion rate than that at $35^{\circ}$C condition. The corrosion rate of stainless steel was almost inedependent of the variation of pH. The significant corrosion rates of carbon steel and the weld joint of carbon-carbon steel were observed at pH 4.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.675-684
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• 2020

An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.131-138
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• 1998

Structural damage is used to be modeled through reductions in the stiffness of structural elements for the purpose of damage estimation of structural system. In this study, the concept of joint damage is employed for more realistic damage assessment of a steel structure. The joint damage is estimated damage based on the mode shape informations using neural networks. The beam-to-column connection in a steel frame structure is represented by a rotational spring at the fixed end of a beam element. The severity of joint damage is defined as the reduction ratio of the connection stiffness with respect to the value of the intact joint. The concept of the substructural identification is used for the localized damage assessment in a large structure. The feasibility of the proposed method is examined using an example with simulated data. It has been found that the joint damages can be reasonably estimated for the case with the measurements of the mode vectors subjected to noise.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.61-72
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• 2011

In this study, the structural details of steel girder-abutment joints with shear connectors and tie bars were suggested to improve the rigid behavior and crack-resisting capacity of the joints in integral bridges. Experimental loading tests of steel girder-abutment joint specimens with the proposed and empirically constructed structural details were carried out, and the capacities and behavioral characteristics of the joints were evaluated through loading tests. Based on the results of the loading tests, it was estimated that all types of tested joints can be applied to the steel girder-abutment joints because they have sufficient stiffness and crack-resisting capacity under the required design and yield loads. According to the initial stiffness, crack propagations, and load-strain relationships, however, the joints with shear connectors and tie bars showed better structural behaviors compared to the empirically constructed joint.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.528-533
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• 2002

The mechanical and metallurgical properties of friction welded joints type 5052 Al alloy/A36 steel have been studied in this paper. The joint strength increased with increasing upset pressure and friction time till it reached the critical value. The joint strength was fixed at low strength compare to that of base metal in the case of increasing friction time. Microstructure of 5052 Al alloy was greatly deformed near the weld interface. The very fine and equaxied grain structure was observed at the near interface. The elongated grain was formed outside dynamic recrystallizatoin region at the peripheral part, while the A36 steel' side was not deformed. The hardness of the near interface was slightly softer than that of 5052 Al alloy base metal. The maximum softening width was about 8mm from the interface. In the present work, the friction welding condition, t$_1$=0.5sec, P$_2$=137.5MPa, showed a maximum joint strength (202MPa) when friction pressure, upset time and rotation speed were fixed at 75MPa, 5sec, 2000rev/min and these were the optimum friction welding condition of 5052Al/A36 steel joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.481-487
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• 2006

Spot-welding is a widely used manufacturing method for thin-sheet components, especially in mass-production industries such as the car industry. Automobiles are often constructed by multi-lap spot welding to secure the passenger from the accident, where optimisation of the welding conditions is a major economic consideration. This research is conducted to investigate weldability characteristics with various welding conditions on the 4-lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to propose the optimum welding conditions. The welding current and the welding time have a greater effect on the welding characteristics than the electrode force. It was found that the electrode force has a relatively close relationship with the expulsion occurrence. The design curves for optimum welding are proposed for the 4-lap spot welded joint.

• Steel and Composite Structures
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• v.38 no.5
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• pp.547-562
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• 2021

This paper aims to explore the mechanical behavior and moment-rotation model of blind bolted joints between concrete-filled double skin steel tubular columns and steel-concrete composite beams. For this type of joint, the inner tube and sandwiched concrete were additionally identified as basic components compared with CFST blind bolted joint. A modified moment-rotation model for this type of connection was developed, of which the compatibility condition and mechanical equilibrium were employed to determine the internal forces of basic components and neutral axis. Following this, load transfer mechanism among the inner tube, sandwiched concrete and outer tube was discussed to assert the action area of the components. Subsequently, assembly processes of basic coefficients in terms of their stiffness and resistances based on the component method by simplifying them as assemblages of springs in series or in parallel. Finally, an experimental investigation on four substructure joints with CFDST columns for validation purposes was carried out to capture the connection details. The predicted results derived from the mechanical models coincided well with the experimental results. It is demonstrated that the proposed mechanical model is capable of evaluating the complete moment-rotation relationships of blind bolted CFDST column composite connections.