• Journal of Welding and Joining
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• v.27 no.5
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• pp.34-41
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• 2009

Thermal and mechanical characteristics in dissimilar SS400-STS304 steel weldment have been investigated by 3D thermal elastic-plastic analysis. Moreover, the influence of welding residual stresses on the mechanical behaviour of this welded joint, by applying superimposed external load (tension load) was determined. The residual stresses obtained by numerical simulation were compared with the experimentally measured results. The FE results were in good agreement with the measured values. The mechanical test (hardness, tensile test) and metallurgical analysis was carried out to ensure the weld integrity. Hence, possibility of applying SS400-STS304 dissimilar steels in industries has been established.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1059-1063
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• 2010

Shimming is an important technique in development of nuclear magnetic resonance (NMR) magnets where image resolution is highly dependent on magnetic field homogeneity. Classically, shimming may be categorized into two types: 1) active shimming that incorporates with extra coils and precise tuning of their currents; and 2)passive shimming that incorporates with pieces of steel placed in a bore of a main magnet and their uniform magnetization under homogeneous external fields. Additional magnetic fields, produced by the coils and/or the steel sheets, compensate original magnetic field from the main magnet in such a way that the total field becomes more homogeneous. In this paper, we developed a passive shimming method based on linear programming optimization. Linear programming is well known to be highly efficient to find a global minimum in various linear problems. We firstly confirmed the linearity of magnetization of ferromagnetic pieces under a presence of external magnetic fields. Then, we adopted the linear programming to find optimized allocation of the steel pieces in the inner bore of a main magnet to improve field homogeneity.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.3
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• pp.447-452
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• 2003

Crevice corrosion is localized form of corrosion usually associated with a stagnant solution on the micro-environmental level. Such stagnant micro environments tend to occur in crevices (shielded areas) such as those formed under gaskets washers insulation material. fastener heads. surface deposits. disbonded coatings. threads. lap joints and clamps. Crevice corrosion is initiated by changes in located electrochemical reaction within the crevice such as a) depletion of inhibitor in the crevice b) depletion of oxygen in the crevice c) a shift to acid conditions in the crevice and d) build-up of aggressive ion species (e.g chloride) in the crevice. In this study. the mechanism of crevice corrosion for Type 430 stainless steel is investigated undercondition that the size of specimen is $15{\times}20\{times}3mm$, in 1N $H_2SO_4$ + 0.05N NaCl solution. and the artificial crevice gap size of 3 x 0.2 x 15 mm. Crevice corrosion is measured under applied potential -300mV(SCE) to the external surface. The obtained result of this study showed that 1) the induced time for initiation of crevice is 750 seconds. 2) potential of the crevice was about from -320mV to -399mV. which is lower than that of external surface potential of -300mV It is considered that potential drop in the crevice is one of mechanisms for the crevice corrosion

• Steel and Composite Structures
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• v.38 no.3
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• pp.319-336
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• 2021

To achieve a rational detail of the girder-abutment joints in composite integral bridges, and validate the performance of the joints with perfobond connectors, this paper proposes two innovative types of I-shaped steel girder-concrete abutment joints with perfobond connectors intended for the most of bearing capacity and the convenience of concrete pouring. The major difference between the two joints is the presence of the top flange inside the abutments. Two scaled models were investigated with tests and finite element method, and the damage mechanism was revealed. Results show that the joints meet design requirements no matter the top flange exists or not. Compared to the joint without top flange, the initial stiffness of the one with top flange is higher by 7%, and the strength is higher by 50%. The moment decreases linearly in both types of the joints. At design loads, perfobond connectors take about 70% and 50% of the external moment with and without top flange respectively, while at ultimate loads, perfobond connectors take 53% and 26% of the external moment respectively. The ultimate strengths of the reduced sections are suggested to be taken as the bending strengths of the joints.

• Steel and Composite Structures
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• v.42 no.2
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• pp.191-207
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• 2022

Undoubtedly, the employment of direct bond interaction between steel and concrete is preceding the other mechanisms because of its ease of construction. However, the large scatter in the experimental data about the issue has hindered the efforts to characterize bond strength. In the following research, the direct bond interaction and bond-slip behavior of CFTs with circular cross-section were examined through repeated load-reversed push-out tests until four cycles of loading. The influence of different parameters including the diameter of the tube and the use of shear tabs were assessed. Moreover, the utilization of expansive concrete and external spirals was proposed and tested as ways of improving bond strength. According to the results section dimensions, tube slenderness, shrinkage potential of concrete, interface roughness and confinement are key factors in a natural bond. Larger diameters will lead to a considerable drop in bond strength. The use of shear tabs by their associated bending moments increases the bond stress up to eight times. Furthermore, employment of external spirals and expansive concrete have a sensible effect on enhancing bonds. Macro-locking was also found to be the main component in achieving bond strength.

• Earthquakes and Structures
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• v.27 no.4
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• pp.251-262
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• 2024

To improve the seismic behavior of composite column with high strength concrete-filled steel tubular in bridge engineering, four column specimens, including one specimen with vertical prestressing force and three specimens with tri-directional prestressing force, were conducted under low cyclic loading. Test parameters including axial compression ratio, degree of vertical prestressing and existence of prestressed steel strips were emphatically analyzed. Experimental results revealed that applying tri-directional prestressing force to column with high strength concrete-filled steel tubular produced more beneficial behavior in terms of ductility, energy-dissipation and self-centering capacity over that of specimens only with vertical prestress. Moreover, ultimate bearing capacity of composite column was improved with increase of degree of vertical prestress and external axial force, while ductility would be reduced. External axial force showed slight influence on the self-centering behavior. Finally, a calculation equation for predicting the shear capacity of the tri-directional prestressed composite column was proposed and the accuracy of the calculated results validated by experimental data.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.143-150
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• 1999

Multipurpose fisheries base was conceptually designed to establish marine ranching system in the coastal waters around Tongyoung, southern sea of Korea. Fisheries base for marine ranching system has integrated various facilities which were required for the process of spawning, rearing, training, releasing, monitoring and catching functions. This base has five steel piles for supporting upper structure and systems. Four steel piles are surrounded by circular net pen made by steel wire, they have the function of the protection against fouling for pile and scouring for bottom soil as well as secondary rearing and short stocking. We can use the last pile to moor a ship and access to the base. Principal structure with steel piles is designed by optimization technique considering design external forces in the coastal waters of return period of 50 years. Design optimization Problem is formulated for this base. Optimal design of multipurpose fisheries base is numerically investigated by sequential quadratic programming method.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.438-441
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• 2004

This paper presents the results of the experimental study on the performances of reinforced concrete beams rehabilitated by external unbonded high tension steel-bar. Design variables for the experiment in this study includes the position of anchorage zone of the high tension steel bar, the anchorage length of the reinforcing steel bar and the types of the shear strengthening measures. 5 specimens were tested with one point monotonically increased loads and structural performances such as strength capacities, ductility capacities and failure modes were analysed. It is found that the structural performance of the rehabilitated beams are strongly depended on the location of anchorage zone of the high tension steel-bars. In the case that anchorage zone is located near the critical shear zone, it is observed that the rehabilitated beam is failed in brittle failure mode and the additional shear strengthening is necessitated. But if anchorage zone is properly located or additional shear strengthening device is provided properly, it is also observed that the strength capacity of the rehabilitated beams could be increased more than $200\%$ by the proposed method.

• Advances in Computational Design
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• v.1 no.1
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• pp.79-86
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• 2016

In this study, the three different meta-heuristics namely the Grey Wolf Optimizer (GWO), Stochastic Fractal Search (SFS), and Adaptive Differential Evolution with Optional External Archive (JADE) algorithms are examined. This study considers optimization of the planer frame to minimize its weight subjected to the strength and displacement constraints as per the American Institute of Steel and Construction - Load and Resistance Factor Design (AISC-LRFD). The GWO algorithm is associated with grey wolves' activities in the social hierarchy. The SFS algorithm works on the natural phenomenon of growth. JADE on the other hand is a powerful self-adaptive version of a differential evolution algorithm. A one-bay ten-story planar steel frame problem is examined in the present work to investigate the design ability of the proposed algorithms. The frame design is produced by optimizing the W-shaped cross sections of beam and column members as per AISC-LRFD standard steel sections. The results of the algorithms are compared. In addition, these results are also mapped with other state-of-art algorithms.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.581-584
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• 2006

This study is analyzed mechanical properties and durability of permeability porous concrete to mix polymer and steel fiber for the enhance of performance and durability of porous concrete. It proves that void ratio and permeability are tallied with internal and external standard of paving porous concrete. A property of strength is increased according as the mixing rate of polymer and steel fiber increase, but it showed the tendency to be reduced on the contrary when mixed upwards of 20% of polymer mixing rate and 0.9vol.% of steel fiber mixing rate. As a result, it is possible to make an enhanced which increased 16% of compressive strength and 30% of flexural strength steel fiber reinforced polymer porous concrete at the mixing rate of 10vol.% of polymer and 0.6% of steel fiber.