• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.354-355
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• 2005

• 콘크리트학회지
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• 제2권3호
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• pp.55-64
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• 1990

구조재료로서 섬유보강콘크리트의 사용이 증가와 더불어 그 자체의 역학적 특성에 대한 더많은 지식이 필요해지고 있다. 본 논문은 단조하중과 반복압축하중을 받을 때 탄소섬유보강콘크리트의 거동에 대한 실험 결과를 나타낸다. 그 결과등은 (1)CFRC는 콘크리트 매트릭스에 섬유를 증가시킴으로써 큰크리트 매트릭스이 강도를 개선시키고 있다. (2) 콘크리트 매트릭스에 섬유를 증가시키는 것은 그 자체의 응력도-변형도 응답에 대해서 실질적인 변화를 가져왔었다. 이 변화는 응력도-변형에도 주목할 정도로 연성이 증가되는 특성이 나타나고 있다. (3) CFRC의 반복하중하에서의 거동은 보통콘크리트에 비해서 더욱 많은 안정성을 가지고 있다. 높은 섬유혼입은 응력도-변형도 곡선에서 곳선하강곡선이 보다 완만하게 나타나고 있다. 이것은 재료의 더 높은 연성의 결과이다.

• Computers and Concrete
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• 제16권2호
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• pp.311-327
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• 2015

Employing discrete elements for considering bond-slip effects in reinforced concrete structures is very time consuming. In this study, a new modified embedded element method is used to consider the bond-slip phenomenon in structural behavior of reinforced concrete structures. A comprehensive parametric study of RC slabs is performed to determine influence of different variables on structural behavior. The parametric study includes a set of simple models accompanied with complex models such as multi-storey buildings. The procedure includes the decrease in the effective stiffness of steel bar in the layered model. Validation of the proposed model with existing experimental results demonstrates that the model is capable of considering the bond-slip effects in embedded elements. Results demonstrate the significant effect of bond-slip on total behavior of structural members. Concrete characteristic strengths, steel yield stress, bar diameter, concrete coverage and reinforcement ratios are the parameters considered in the parametric study. Results revealed that the overall behavior of slab is significantly affected by bar diameter compared with other parameters. Variation of steel yield stress has insignificant impact in static response of RC slabs; however, its effect in cyclic behavior is important.

• 대한기계학회논문집A
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• 제31권12호
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• pp.1165-1172
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring, nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. Shape optimization of the spring is carried out based on EL. The objective function is defined by minimizing the maximum stress in the spring while mass is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear response analysis. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.482-485
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• 2006

The response of a reinforced concrete element under cyclic shear is characterized by the hysteretic loops of the shear stress-strain curves. These hysteretic loops can exhibit strength deterioration, stiffness degradation, and a pinched shape. Recent tests have shown that the orientation of steel grids in RC shear elements has a strong effect on the "pinching effect" in the post-yield hysteretic loops. When the steel grid was set at a 45 degree angle to the shear plane, there was no pinching effect and no strength deterioration. However, when the steel grid was set parallel to the shear plane, there was a severe pinching effect and severe strength deterioration with increasing shear strain magnitude. In this paper, two RC elements subjected to revered cyclic shear stresses are considered to study the effect of the steel grid orientation. The presence and absence of the pinching mechanism in the post-yield shear hysteretic loops is studied using the Rotating Angle Softened Truss Model (RA-STM) theory.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.182-189
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• 2000

This paper presents a simple and reliable constitutive model for predicting the nonlinear response of reinforced concrete subjected to general membrane loadings. Based on the concept of equivalent uniaxial strain, constitutive relations of concrete are presented in the axes of orthotropy. The behavior of cracked concrete is described by a system of orthogonal cracks, which follows the principal strain directions and rotates according to the loading history. Simple hysteretic rules defining the cyclic stress-strain curves of concrete and steel are used. In addition, the stiffness and strength degradation of cracked concrete is included in the formulation. Correlation studies between analytical results and experimental values from idealized shear panel tests are conducted with the objective to establish the validity of the proposed model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• 한국구조물진단유지관리공학회 논문집
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• 제14권5호
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• pp.161-168
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• 2010

실무 및 연구에 있어서 반복하중을 받는 콘크리트 벽체의 변형 및 저항능력 그리고 재료의 변형율 등을 정확하게 평가할 수 있는 방법이 필요하다. 따라서 본 논문에서는 비선형 트러스 부재를 이용하여 반복 횡하중을 받는 철근콘크리트 벽체 또는 철근콘크리트 면부재를 모델링 하였다. 콘크리트와 배근된 철근은 각각 수직, 수평 그리고 대각선 비선형 부재를 이용해 모델링 되었다. 본 논문에서는 높이/폭 비가 1.2인 벽체를 예제로 선택하여 실험의 결과와 비교하였다. 비교를 위하여 주대각선 부재의 경로에 따른 4가지의 형상과 대각선 부재들의 배열에 따른 3가지 형상이 채택되어 실험 결과와 가장 근사한 모델링의 선택을 위해 평가를 실시하였다.

• Structural Engineering and Mechanics
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• 제89권3호
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• pp.239-252
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• 2024

Steel plate shear walls (SPSWs) are classified as lateral load-resisting systems. The feasibility of openings in the steel plate is a characteristic of SPSWs. The use of openings in SPSWs can lower the load capacity, stiffness, and energy dissipation. This study proposes a novel form of SPSWs that provides convenient access through openings by combining steel plates and eccentrically braced frames (EBFs). The proposed system also avoids a substantial reduction in the strength and stiffness. Hence, various geometric forms were analyzed through two different structural approaches. Groups 1, 2, and 3 included a steel EBF with a steel plate between the column and EBF in order to improve system performance. In Group 4, the proposed system was evaluated within an SPSW with openings and an EBF on the opening edge. To evaluate the performance of the proposed systems, the nonlinear finite element method (NL-FEM) was employed under cyclic loading. The hysteresis (load-drift) curve, stress contour, stiffness, and damping were evaluated as the structural outputs. The numerical models indicated that local buckling within the middle plate-EBF connection prevented a diagonal tension field. Moreover, in group 4, the EBF and stiffeners on the opening edge enhanced the structural response by approximately 7.5% in comparison with the base SPSW system.

• 한국지반공학회논문집
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• 제18권1호
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• pp.91-99
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• 2002

본 연구에서는 변형률 수준별 실내진동시험 및 지진응답해석의 수행을 기초로 하는 새로운 액상화 평가법을 제안하였다. 제안된 평 가법에서는 비 배수조건 하에서 진동전단하중으로 야기된 과잉간극수압의 누적으로 액상화가 발생하는 점을 고려하여 진동하중을 받는 포화지반의 액상화 거동을 실내진동시험결과의 전단응력-전단변형률 이력곡선을 토대로 산정한 교란도와 소성 전단변형률 상각궤도의 변화로 정의하였으며, 이를 실지진 시간이력의 지반 내 거동변화와 연계시킴으로써 지진이 보유한 연속성 및 불규칙성을 합리적으로 고려하도록 하였다. 또한, 제안된 평가법에서는 진동하중의 변화에 관계없이 액상화 발생시 포화사절토의 동적특성은 일정하다는 일련의 연구사례를 토대로 내친 해석시 이용되는 전변형률 수준의 동적물성 획득시험만으로도 액상화 평가가 가능하도록 하였으며 정현하중의 크기를 달리한 진동삼축시험에서 산정된 액상화 발생시의 소성 전단변형률 상각궤도를 비교함으로써 이에 대한 검증연구를 수행하였다. 연구결과, 진동정현하중의 크기에 관계없이 액상화 발생시 지반의 동적특성 치가 유일한 값을 나타내었다 그러므로, 제안된 평가법은 변형률 수준별 실내진동시험을 통해 지반의 동적물성 획득과 액낭화 평가 수행이 가능할 뿐만 아니라, 지진응답해석을 통해 불규칙한 실지진 시간이력 전부를 고려하는 특징으로 육상화 평가결과의 신뢰성을 향상시킬 수 있을 것으로 판단된다.