• Journal of Korean Society of Steel Construction
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• v.8 no.3 s.28
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• pp.35-45
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• 1996

The purpose of this paper is to investigate experimentally the strength and deformation of T-joints to improve the structural behavior of truss connection consisted in square hollow steel section. There are two-types to be changed in T-joint shape. One type is TP-series that a brace member is rotated to 45 degree, another type is TR-series that a chord member is rotated to 45 degree. The most important results obtained from the 2nd experiment on the T-joints is as follow; The yielding strength and initial stiffness of TP-series increase more than a current type(TS-series) in $0.6{\leq}{\beta}(d/D){\leq}0.7(0.85{\leq}{\beta}$'$(={\sqrt2}{\cdot}{\beta}){\leq}1.0)$.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.773-790
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• 2013

Bending behaviors of corroded reinforced concrete (RC) beams under repeated loading were investigated experimentally. A total of twenty test specimens, including four non-corrosion and sixteen corrosion reinforced concrete beams, were prepared and tested. A numerical model for flexural and cracking behaviors of the beam under repeated loading was also developed. Effects of steel corrosion on reinforced concrete beams regarding cracking, mid-span deflection, stiffness and bearing capacity of corroded beams were studied. The impact of corrosion on bond strength as the key factor was investigated to develop the computational model of flexural capacity. It was shown from the experimental results that the bond strength between reinforcement and concrete had increased for specimen of low corrosion levels, while this effect was changed when the corrosion level was higher. It was indicated that the bearing capacity of corrosion beam increased even at a corrosion level of about 5%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• The Journal of Korea Robotics Society
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• v.3 no.2
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• pp.146-153
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• 2008

본 논문에서는 인간 운동 제어 이론과 기계학습을 기반으로 하여 로봇의 접촉 작업 수행을 위한 새로운 운동 학습 전략을 제시하였다. 성공적인 접촉 작업 수행을 위한 본 연구의 전략은 강화학습 기법을 통하여 최적의 작업 수행을 위한 임피던스 매개 변수를 찾는 것이다. 본 연구에서는 최적의 임피던스 매개 변수를 결정하기 위하여 Recursive Least-Square (RLS) 필터 기반 episodic Natural Actor-Critic 알고리즘이 적용되었다. 본 논문에서는 제안한 전략의 효용성을 증명하기 위해 동역학 시뮬레이션을 수행하였고, 그 결과를 통하여 접촉작업에서의 작업 최적화 및 환경이 가지는 불확실성에 대한 적응성을 보여 주었다.

• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1253-1269
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• 2015

The present paper investigates the post heating behavior of concrete beams reinforced with fiber reinforced polymer (FRP) bars, namely carbon fiber reinforced polymer (CFRP) bars and glass fiber reinforced polymer (GFRP) bars. Thirty rectangular concrete beams were prepared and cured for 28 days. Then, beams were either subjected (in duplicates) to elevated temperatures in the range (100 to $500^{\circ}C$) or left at room temperature before tested under four point loading for flexural response. Experimental results showed that beams, reinforced with CFRP and GFRP bars and subjected to temperatures below $300^{\circ}C$, showed better mechanical performance than that of corresponding ones with conventional reinforcing steel bars. The results also revealed that ultimate load capacity and stiffness pertaining to beams with FRP reinforcement decreased, yet their ultimate deflection and toughness increased with higher temperatures. All beams reinforced with FRP materials, except those post-heated to $500^{\circ}C$, failed by concrete crushing followed by tension failure of FRP bars.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.1
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• pp.42-50
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• 1987

The energy expressions are formulated for the axially stiffened shell treating the stiffeners as discrete elements. The principle of minimum potential energy is employed to formulate the buckling equations for a simply supported, axially stiffened shell under uniform axial compression. The displacement functions are expended into double trigonometric series. The mode assuming method employed in this paper makes it possible to reduce the matrix size of the eigenvalue problem considerably. Effects are made to investigate the transition from overall buckling to local buckling and to verify the existence of the minimum stiffness ratio of stiffener as in the case of stiffened plate. The results of the calculation show that the critical stiffener size increase linearly as the length of the shell increases. The results also show that the overall buckling load decreases and the local buckling load has a nearly constant value as the length of the shell increases. The results show very good agreements with other computational available.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.127-130
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• 2005

The purpose of this study is to investigate the flexural behavior of reinforced concrete beam members exposed to high temperature. In order to study the flexural behaviors, the 17 specimens have been tested with variables of reinforcement ratios($0.5\rho_{max},\rho_{min}$), heating conditions(nonheating, 400$^{circ}C$, 600$^{circ}C$, 800$^{circ}C$ heating and 1 hour preservation) and loading state(stressed and residual state). The results show that the stiffness and strength of specimens are lower when they are exposed to higher temperature and the pattern of crack and color of specimens exposed to fire are different from ordinary concrete members.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.79-82
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• 2005

This study reports on the structural characteristics of slab-column connections using an ultra-high-strength-fiber-reinforced concrete from new and retrospective data. The parameters investigated were the ' puddling ' of ultra-high-strength-fiber-reinforced concrete and the use of high-strength concrete in the slab. The effects of these parameters on the punching shear capacity, negative moment cracking, and stiffness of the two-way slab specimens are investigated. Furthermore, the ACI Code (2002), the CSA Standard (1994), the BS Standard (1985) and the CEB-FIP Code (1990) predictions are compared to the experimental results obtained from some slab-column connections tested in this experiment and those tested by other investigators. The beneficial effects of the ultra-high-strength-fiber-reinforced concrete puddling and of the use of high-strength concrete are demonstrated. It is also concluded that the punching shear strength of slab-column connections is a function of the flexural reinforcement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.503-506
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• 2005

The purpose of this study was the Development of Retrofit Method for Beam Using Steel Plate Reinforced by Fiber Sheet.1. Additional reinforcements are not needed in the joining area of slab and beam web.2. Beam using carbon fiber reinforced plastic displays low effects in shearing effect.3. Beams reinforced steel plate by epoxy effect the capacities of strength. But the capacities of strength are rapidly reduced when adhesive surface be omitted. Thus details are needed in this case.4.Retrofit method for beam using steel plate reinforced by fiber sheet with epoxy rosin improves the capacities of strength and the initial stiffness, shows a large transformation since the maximum load likewise may be excellent to the shearing reinforcement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.21-22
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• 2015

The CFT(Concrete Filled Tube) system has been developed to behave well in a structural performance such as stiffness, stress, ductility, fire resistance that is derived from its mechanical advantages of composite structure. There were number of studies about unprotected CFT columns for improving their fire resistance through reinforcing bars or plates being placed inside the steel tube. It was also known that reinforcing plates of flat type need stiffeners in a certain distance to avoid their buckling failure so it cost as much as their using consequentially. This paper is planned to test the work of beam elements attached inner side of CFT depending on its shape. More discussions on beam's design could be followed after some fire tests accordingly conducted within this project.