• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.41-44
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• 2004

This experimental investigation was conducted to examine the behaviour of eight one-third scale columns made of high-strength concrete (HSC). The columns were subjected to a constant axial load corresponding to 30 per cent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement, tie configuration and tie yield strength. Columns with 42 per cent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour. Relationships between the calculated damage index and the observed damage such as initial crack, spalling of concrete, buckling of longitudinal bar, and crushing of concrete are propose.

• Structural Engineering and Mechanics
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• 제64권5호
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• pp.671-681
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• 2017

This study investigates the structural performance of 3D steel pipe rack suspended scaffolding systems. For the purpose, a standard full scale 3D steel pipe rack suspended scaffolding system considering two frames, two plane trusses, purlins and wooden floor is constructed in the laboratory. A developed load transmission system was placed in these experimental systems to distribute single loads to the center of a specific area in a step-by-step manner using a load jack. After each load increment, the displacements are measured by means of linear variable differential transducers placed in several critical points of the system. The tests are repeated for five different system conditions to determine the structural performance. The means of system conditions is the numbers of the tie bars which are used to connect plane trusses under level. Finite elements models of the 3D steel pipe rack suspended scaffolding systems considering different systems conditions are constituted using SAP2000 software to support the experimental tests and to use the models in future studies. Each of models including load transmission platform is analyzed under a single loading and the displacements are obtained. In addition, to calibrate the numerical models some uncertain parameters such as elasticity modulus of wooden floor and connection rigidity of purlins to plane trusses are assessed experimentally. The results of this work demonstrate that when increasing numbers of tie bars the displacement values are decreased. Also the results obtained from developed numerical models have harmony with those of experimental. In addition, the scaffolding system with two tie bars at the beginning and at the end of the plane truss has the optimum structural performance compared the results obtained for other scaffolding system conditions.

• 콘크리트학회논문집
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• 제15권3호
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• pp.417-424
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• 2003

철근콘크리트 기둥-철골보(RCS)합성골조 접합부에서 지압 거동을 평가하고 지압설계를 위하여 단순화한 국부지압 실험을 수행하였다. 편심하중에 의해 국부지압을 받을 때 콘크리트의 쐐기작용과 띠철근의 횡구속 효과에 의해 저항된다. 실험결과 U형 지압보강근은 지압내력을 철근 강도만큼 증가시키면서 상세와 설치가 단순하여 효과적으로 나타났다. 띠철근 양에 따라 지압강도가 증가하며 이중 띠철근이 더욱 효과적으로 약20% 증가된다. 현행 ASCE설계지침에서 띠철근 규정은 지압내력이 2 $f_{ck}$ 가 되기 위해서는 다소 미흡하며, 지압강도는 띠철근과 이중 띠철근을 증가시킴에 따라 최대한 2.5 $f_{ck}$ 까지 사용할 수 있다. 본 연구의 결과로서 RCS 보기둥 접합부의 지압내력 추정을 위한 예측식이 제안되었으며 실험결과와 비교적 잘 일치되고 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.517-520
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• 1999

In this study, the problem of strengthening of reinforced concrete (RC) columns by a central steel section with minimum amount is taken up. For this purpose, RC columns with central reinforcing elements such as a steel bar, a steel H section and a steel pipe were taken up. To certify the effect of this way of reinforcing, experimental study using specimens of RC columns of shear span ratio of 2.5 was carried out. The variables which are considered to affect the behavior of RC columns subjected to axial load and cyclic shear load are the magnitude of axial load, tie ratio and main bar ratio. As the results of this study, the effect of a central reinforcing element for making higher the earthquake resistant properties of RC columns were observed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.67-70
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• 2005

In this study, an experimental investigation of the strength of R/C columns with 300mm square sections confined by head anchorage bar is presented. This initial phase of research considers only axial loading and consists of a total of 7 column tests. The main variables are distance and anchorage type of transverse reinforcement such as standard hooks and headed bar. The purpose of this study is to investigate the confinement effect and strength increment by head and to propose the confinement model for column using the head at end of lateral tie. Also, the test results for ultimate strength and strength gain factor of columns in this study and previous study is compared with the existing analytical models. Based on the test results, the Saatcioglu's model estimates confinement effects was closed to experimental value and the developed analytical approach considered the head was capable of predicting the strength gain factor results with a resonable accuracy.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.291-293
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• 2003

Applicability and economical feasibility of a Superconducting Fault Current Limiter (SFCL) have been investigated using the PSS/E simulation for a bus bar coupling at the real 154 ㎸ KEPCO power grid near Seoul. For the investigated substation, the maximum fault current exceeds the interruption rating of 4 circuit breakers (CB) out of 9 installed in the substation. The simulation showed that a SFCL installed in the bus tie position effectively limits the fault currents to save 4 CBs, which are to be replaced by ones of gloater interruption rating, otherwise. We suggest that the optimum resistance of the SFCL be 10 Ohm for the given grid.

• 한국도로학회논문집
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• 제16권4호
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• pp.1-9
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• 2014

PURPOSES: The objective of this study is to evaluate construction issues and design for transverse steel in continuously reinforced concrete pavement(CRCP). METHODS : The first continuously reinforced concrete pavement(CRCP) design procedure appeared in the 1972 edition of the "AASHTO Interim Guide for Design of Pavement Structures", which was published in 1981 with Chapter 3 "Guide for the Design of Rigid Pavement" revised. A theory that was accepted at that time for the analysis of steel stress in concrete pavement, called subgrade drag theory(SGDT), was utilized for the design of reinforcement of CRCP - tie bar design and transverse steel design - in the aforementioned AASHTO Interim Guide. However SGDT has severe limitations due to simple assumptions made in the development of the theory. As a result, any design procedures for reinforcement utilizing SGDT may have intrinsic flaws and limitations. In this paper, CRCP design procedure for transverse steel was introduced and the limitations of assumptions for SGDT were evaluated based on various field testing. RESULTS: Various field tests were conducted to evaluate whether the assumptions of SGDT are reasonable or not. Test results show that 1) temperature variations exist along the concrete slab depth, 2) very little stress in transverse steel, and 3) warping and curling in concrete slab from the field test results. As a result, it is clearly revealed out that the assumptions of SGDT are not valid, and transverse steel and tie bar designs should be based on more reasonable theories. CONCLUSIONS : Since longitudinal joint is provided at 4.1-m spacing in Korea, as long as joint saw-cut is made in accordance with specification requirements, the probability of full-depth longitudinal cracking is extremely small. Hence, for transverse steel, the design should be based on the premise that its function is to keep the longitudinal steel at the correct locations. If longitudinal steel can be placed at the correct locations within tolerance limits, transverse steel is no longer needed.

• 한국도로학회논문집
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• 제8권4호
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• pp.25-36
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• 2006

본 연구에서는 콘크리트포장 확장접속부의 추적조사를 통해 시공 및 설계상의 문제점을 확장구간의 평탄성 저하, 진동이 콘크리트에 미치는 영향, 접속부의 접속불량의 관점에서 분석하였다. 기존 측대 일부분만 절단한 경우 접속부에 윤하중이 반복 집중되어 종종 과도한 벌어짐과 단차로 이어지는 것이 목격되었다. 또한 팻칭된 부분에 균열이 재 발생되는 모습도 관찰하였다. 2004년 같은 시기에 신설 준공된 구간과 평탄성을 비교한 결과 확장 준공된 구간의 평탄성 값이 다소 높게 나타났다. 확장구간 설계 시 3차선 4차선으로 확장하는 경우 기존 구간에 설치된 타이바의 내력이 부족해지는 경우에 대해 설명하였다. 현행 타이바를 시공하는 방법에 의한 타이바의 정착강도가 소요강도의 57%에 불과하므로 대안을 제시하였다.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.1630-1638
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• 2015

많은 산업분야에서 구조설계 시 구조성능을 검토하기 위한 유한요소해석은 필수적인 과정이 되었다. 이와 함께, 컴퓨터의 성능도 급속도로 개선되고 있지만 대형 문제의 경우에는 최적설계기법을 적용하는데 한계가 있다. 이러한 대형 문제의 최적화를 위하여 메타모델을 이용한 근사모델을 이용하고 있다. 근사모델을 생성하는 방법은 곡선맞춤법과 내삽법으로 분류할 수 있는데, 반응표면모델과 크리깅 모델이 대표적인 것이다. 그러나 각 모델은 오버피팅이나 언더피팅이 될 수 있는 단점이 있다. 본 연구에서는 반응표면과 크리깅으로 구성되는 혼합모델에 의한 메타모델을 이용하여 구조설계에 적용하고자 한다. 제안된 방법을 2부재 구조물과 자동차용 아우터타이로드의 구조설계에 적용하였다.

• Earthquakes and Structures
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• 제7권5호
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• pp.843-859
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• 2014

In the present study, the seismic performance of structural walls with boundary elements confined by conventional tie hoops and steel fiber concrete (SFC) was investigated. Cyclic lateral loading tests on four wall specimens under constant axial load were performed. The primary test parameters considered were the spacing of boundary element transverse reinforcement and the use of steel fiber concrete. Test results showed that the wall specimen with boundary elements complying with ACI 318-11 21.9.6 failed at a high drift ratio of 4.5% due to concrete crushing and re-bar buckling. For the specimens where SFC was selectively used in the plastic hinge region, the spalling and crushing of concrete were substantially alleviated. However, sliding shear failure occurred at the interface of SFC and plain concrete at a moderate drift ratio of 3.0% as tensile plastic strains of longitudinal bars were accumulated during cyclic loading. The behaviors of wall specimens were examined through nonlinear section analysis adopting the stress-strain relationships of confined concrete and SFC.