• Proceedings of the KWS Conference
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• 2010.05a
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• pp.67-67
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• 2010

최근 전 세계적으로 유가상승 및 환경에 대한 관심이 증대되면서 자동차 업계에서는 차량 경량화를 통한 연비향상에 대한 연구가 활발히 진행되고 있다. 대표적인 차량 경량화 방법으로 초경량 철강 차체의 개발을 들 수 있는데 이는 고강도강을 차체에 적용함으로써 강성을 증대시킴과 동시에 두께 감소에 의한 경량화를 이루는 방법이다. 하지만 고강도강은 자체의 높은 강성을 지니는 반면 첨가된 합금원소에 의하여 용접성이 떨어지는 제약을 가지고 있다. 펄스 GMA 용접은 One Drop Per Pulse (ODPP) 의 안정된 용적 이행으로 스패터 발생이 거의 없으며 일반 GMA 용접에 비하여 용접성이 우수하여 자동차 차체 조립공정에 적용되고 있다. 본 연구에서는 440MPa 급 도금, 비도금 강판 및 이종 강판의 겹치기 용접 실험을 통해 강종별, 두께별 펄스 아크 용접에 대한 용접성 평가 및 데이터 베이스를 구축하고자 하였다. 용접부 단면마크로, 인장시험, 경도시험을 통해 적정 용접영역을 확보하였으머, 고속카메라 촬영을 통해 보호가스에 따른 용적 이행 현상을 확인하였다.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.219-228
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• 2010

This paper describes an experimental research on the structural behavior and the ultimate strength of longitudinally stiffened plates subjected to local, distortional, or mixed-mode buckling under compression. The stiffened plate undergoes local, distortional, or interactive local-distortional buckling according to the flexural rigidity of the plate's longitudinal stiffeners and the width-thickness ratios of the sub-panels of the stiffened plate. A significant post-buckling strength in the local and distortional modes affects the ultimate strength of the longitudinally stiffened plate. Compression tests were conducted on stiffened plates that were fabricated from 4mm-thick SM400 steel plates with a nominal yield stress of 235MPa. A simple strength formula for the Direct Strength Method based on the test results was proposed. This paper proves that the Direct Strength Method can properly predict the ultimate strength of stiffened plates when the local buckling and distortional buckling occur simultaneously or nearly simultaneously.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.481-492
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• 2018

The steel-plate concrete composite beam is composed of a steel plate, concrete and shear connector to combine two inhomogeneous materials. In general, the steel plate is assembled by welding an existing composite beam. In this study, the SPC beam was composed of folding steel plates and concrete, without a headed stud. The folding steel plate was assembled by a high strength bolt instead of welding. To improve the workability in a field construction, a hat-shaped cap was attached to the junction with a slab. Monotonic load testing under two points was conducted under displacement control mode to analyze the flexural strength of the SPC beam using a cap as the shear connector. Five specimens with shear connector types, protrusion length, and different thickness of steel plates were constructed and tested. The experimental results were analyzed through the relationship between the shear strength ratio and flexural strength in KBC 2009. The test results showed a shear strength ratio of more than 40 %. In the case of using a cap-like specimen as the shear connector, the flexural strength was 70% of the value calculated as a fully composite beam. In addition, the cap showed a smaller shear strength than the stud, but the cap served as a shear connection. When the thickness of the steel plate was taken as a variable, the steel plate exhibited a bending strength of approximately 70% compared to a fully formed steel plate, and exhibited similar deformation performance. Local buckling occurred due to incomplete composite behavior, but local buckling occurred at a 5% higher strength for a relatively thick steel plate. The buckling width also decreased by 15%.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.471-481
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• 2009

The purpose of this study was to compare and analyze the compression behaviors of SSC (stiffened steel plate-concrete) and NSC (non-stiffened steel plate-concrete) structures, and to identify the effects of the increment in the structural performance of SSC structures. SCC structures are structures that integrate steel plates with line support from ribs (H-shape) and point supports from studs with concretes. On the other hand, NSC structures are structures that integrate steel plates with point supports from studs with concrete. The following results were obtained in this study. First, compared with NSC structures, it was shown that SSC structures have advantages in terms of preventing steel plate buckling and delaying quick destruction through the brittleness of concrete. In addition, the SSC structures showed a 5-28% increment in maximum compressive strength, which far surpassed that shown by the NSC structures.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.725-735
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• 2007

The local buckling strength and post-local buckling strength of thin steel plates in the steel-concrete composite column were evaluated by nonlinear finite element analyses. The proposed width-to-thickness limit ratio was based on elastic buckling analyses, in which the increased local buckling capacity of the plate due to the in-filled concrete was considered by the boundary conditions of the thin plate. Considering the initial imperfections and residual stresses, we determined the initial local buckling strength and post-local buckling strength of the thin plates with various width-to-thickness ratios. The formula to evaluate the compressive capacity of the steel-concrete composite column based on the effective width of the plate was proposed. For verification, values determined by the formula were compared with the experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.116-122
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• 2021

This study quantitatively evaluated the performance improvement of a circular reinforced concrete pier under dynamic load with strengthening using a steel plate. Various three-dimensional elements were applied using the finite element program ABAQUS. The analytical parameters included the ratios of the steel cover length to the pier's total height and the ratios of the steel cover thickness to the pier diameter for inelastic-nonlinear analysis. The lower part of the pier had fixed boundary conditions, and lateral repetitive loads were applied at the top of the pier. The pier was investigated to evaluate the dynamic performance based on the load-displacement curve, stress-strain curve, ductility, energy absorption capability, and energy ratio. The yield and ultimate loads of piers with steel covers increased by 3.76 times, and the energy absorption capability increased by 4 times due to the confinement effects caused by the steel plate. A plastic hinge part of the column with a steel plate improved the ductility, and the thicker the steel plate was, the greater the energy absorption capacity. This study shows that the reinforced pier should be improved in terms of the seismic performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.77-80
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• 2008

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. This research aims at evaluating the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal steels, which were strengthened with prestressed steel jacket in the plastic hinge region. Quasi-static test was used to investigate the seismic performance enhancement of RC test specimens. Conventional method applied mortar grouting inside steel jacket, but this research did not apply mortar grouting inside steel plate. Four test specimens in an aspect of 3.5 were constructed with 400 mm in diameter and 1600 mm in height. Test parameters are the lap splice of longitudinal reinforcing steels and thickness of steel jacket.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.384-384
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• 2013

본 연구에서는 e-beam 증착을 이용하여 Al, Mg 단일 금속으로 다층형 Al-Mg 코팅층을 제조하여 특성 분석 및 내식성을 평가하였다. Al-Mg 코팅층은 99.99%의 Al, 99.9%의 Mg grain을 사용하여 E-Beam 가열을 통해 냉연강판 위에 코팅하였다. 증발물질과 기판과의 거리는 48 cm이며, 기판은 세척을 실시한 후 진공 챔버에 장착하고 ~10-5 Torr 까지 진공배기를 실시하였다. 진공챔버가 기본 압력까지 배기되면 아르곤 가스를 주입하고 기판홀더에 800 V의 직류 전압을 인가하여 약 30분간 글로우 방전 청정을 실시하였다. 기판의 청정이 끝나면 아르곤 가스를 차단하고 코팅층의 구성형태에 따라 Al 또는 Mg을 코팅하였다. 다층형 Al-Mg 코팅층은 2층에서 최대 6층까지 제조하였으며 $3{\mu}m$의 두께를 기준으로 Al과 Mg 코팅층의 두께비가 각각 1:1 과 2:1이 되도록 코팅하였다. 6층 이상에서는 코팅층의 두께 제어가 쉽지 않기 때문에 층수는 6층으로 제한하였다.다층형 Al-Mg 코팅층을 주사전자현미경으로 관찰한 결과, Al-Mg 코팅층간의 계면을 관찰할 수 있었다. 또한 글로우방전분광기로 Al-Mg 코팅층을 관찰한 결과, Al과 Mg 코팅층이 균일한 다층 구조를 형성하고 있는 것을 확인할 수 있었다. 다층의 Al-Mg가 코팅된 강판을 염수분무시험을 통해서 내부식 특성을 확인하였다. Al-Mg 코팅 강판의 염수분무시험 결과, Al-Mg 코팅층의 층수가 증가할 수록 내부식 특성이 향상되는 것을 확인할 수 있었으며, 이러한 현상은 Al-Mg 코팅층이 다층으로 형성되어 있어 부식 생성물을 효과적으로 차단하여 강판의 부식을 방지한 것으로 판단된다.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.269-278
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• 2008

The primary object of the paper is to understand the compressive buckling characteristics of steel-concrete structures through the finite element analysis. The buckling pattern, compressive strength and stiffness of the steel plate concrete structures were investigated by the FEM analysis using the variations of B/t ratios and stud pitches. The investigation was focused on steel plate concrete structures with and without ribs placed on the surface of steel plates. The results of the FEM analysis were compared with the previous results from the theoretical equations. Conclusively, the buckling of the steel plate concrete structures occurred in the transverse direction of the loading direction. The stiffness of the steel plate concrete structure with ribs is greater than the one without the stiffened rib. The compressive strength in the FEM analysis is similar to that of JEAG 4681 and it showed 20% greater value than that of the proposed equations.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.707-715
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• 2005

Corrugated webs have been used for composite prestressed concrete box girder bridges. Innovative steel plate girders using corrugated webs have been proposed. It has been found that analytical and experimental researches conducted to determine the strength of trapezoidally corrugated webs can fail with respect to three different buckling modes: local, global, and interactive shear buckling. Shear buckling capacity equations based on classical and orthotropic plate buckling theories have been proposed,but these equations show some differences. In this paper, geometric parameters that influence interactive shear buckling behavior with interaction effects are identified via extensive bifurcation buckling analysis using the finite element meth.