• 한국지반공학회논문집
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• 제25권4호
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• pp.39-54
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• 2009

대형직접전단시험기를 이용하여, 국내의 석산에서 생산된 쇄석재료들에 대한 전단거동을 분석하였다. 시료별로 전단강도를 산출하였으며, 최대입경, 수침조건, 밀도, 균등계수, 파쇄율 등의 변화에 따른 전단거동의 영향을 평가하여, 선행연구결과와 정성적으로 비교하였다. 아울러, 일의 원리를 응용하여, 쇄석재료의 응력-다일러턴시 관계를 규명하였으며, 한계상태의 마찰계수와 첨두마찰각 및 팽창각을 산출하였다. 실험결과 일축압축강도와 파쇄율이 쇄석의 내부마찰각에 가장 결정적인 영향을 미치며, 파괴시 다일러턴시도 연관성이 높은 것으로 밝혀졌다.

• 한국지반공학회논문집
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• 제25권10호
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• pp.41-53
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• 2009

조립재료의 입자 형상이 입자 파쇄 전개 및 전단 거동 특성에 미치는 영향을 분석하기 위하여, 개별요소법(DEM, discrete element method)을 이용하여 직접전단시험을 수치해석적으로 모델링하였다. PFC(Particle Flow Code)내의 clump 모델 및 cluster 모델을 이용하여 6가지 형상의 입자를 생성하여 이를 원형입자의 직접 전단거동과 비교 분석함으로써 입자형상의 영향을 연구하였다. 연구결과, PFC에 의해 모델링된 직접 전단모델의 수치해석 결과는 실내 실험결과와 잘 일치하였으며, 따라서 본 연구 결과의 타당성을 입증하였다. 입자 형상 관점에서 모나고 거친 입자의 내부마찰각이 상대적으로 둥글고 매끄러운 입자에 비해 큰 값을 나타냈으며, 입자 파쇄 또한 많이 발생하는 것을 확인하였다. 이때 입자파쇄는 전단면근처에 집중되며 전단대를 형성하였다. 따라서 본 연구에서 제시한 수치해석 모델은 향후입자 파쇄를 포함한 조립재료의 전단강도 특성 연구에 다양하게 적용될 수 있다고 판단된다.

• Steel and Composite Structures
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• 제53권1호
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• pp.29-43
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• 2024

In this paper, the behavior of an innovative metallic a butterfly-shaped link as damper with shear and flexural mechanism was investigated experimentally and numerically. The damper is directly attached to the diagonal member of the Concentrically Braced Frame (CBF) to prevent buckling of the braces. Since it is expected that nonlinear behavior of the system is limited to the dampers, the other parts of structures remind elastic that the damper can replaced easily after a severe earthquake. The experimental outcomes indicated that both types of dampers (with shear or flexural mechanism) pertain to stable hysteresis loops without any significant degradation in stiffness or strength. Comparing the dampers indicated that the shear damper has a greater ultimate strength (4.59 times) and stiffness (3.58 times) than flexural damper but a lower ductility (16%) and ultimate displacement (60%). Also, the shear damper has a considerable dissipation energy 14.56 times greater than flexural dampers where dissipating energy are affected by ultimate strength, stiffness and ultimate displacement. Also, based on the numerical study, the effect of main plate slenderness on the behavior of the damper was considered and the allowable slenderness was suggested to the design of the dampers. Numerical results confirmed that the flexural damper is more sensitive to the slenderness than shear damper. Accordingly, as the slenderness is less than 50 and 30, respectively, for, shear and flexural damper, no degradation in ultimate strength is realized. By increasing the slenderness, the maximum reduction of the ultimate strength, stiffness, and energy dissipation capacity reached by 16%, 7%, and 17% for SDB dampers whereas it is 3%, 33%, 20%, and 45% for MDB.

• 터널과지하공간
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• 제33권6호
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• pp.574-593
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• 2023

본 연구에서는 절리면 암석 시료에 대한 직접 전단시험을 수행하기 위해 새로 고안된 Compact CNS shear box의 성능과 적용 가능성에 대해 조사하였다. 정적 CNS 절리면 직접 전단시험은 인공적으로 거칠기를 생성한 절리 암석을 대상으로 실시하였으며 절리면 거칠기 계수 및 초기 수직응력 조건을 변화시키면서 수행하였다. 또한, DIC 분석을 통해 변위 데이터 검증 및 파괴 패턴을 관찰하였고 실험으로부터 도출된 전단 특성들을 기존에 연구되었던 전단 거동 예측 모델들과 비교분석하였다. 그 결과 기존의 특정 경험적 전단 거동 예측 모델과 높은 상관관계를 나타내는 것을 확인하였으며 전단 거동 특성이 파괴 패턴과 관련이 있을 가능성에 대해 고찰하였다. 결론적으로, 절리면 전단 특성에 대한 데이터를 제공하는데 있어서 CNS 전단 박스의 적용 가능성과 효과를 입증하였다.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.741-754
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• 2014

The conventional PHC pile-footing connection is the weak part because the surface area and stiffness are sharply changed. The Composite PHC pile reinforced with the transverse shear reinforcing bars and infilled-concrete, hereafter ICP pile, has been developed for improving the flexural and shear performance. This paper investigates the cyclic behavior and performance of the ICP pile-footing connection. To investigate the behavior of the connection, one PHC and two ICP specimens were manufactured and then a series of cyclic loading tests were performed. From the test results, it was found that the ICP pile-footing connection exhibited higher cyclic behavior and connection performance compared to the conventional PHC pile-footing connection in terms of ductility ratio, stiffness degradation and energy dissipation capacity.

• 한국항공운항학회지
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• 제14권3호
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• pp.16-22
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• 2006

The friction and wear of tire determined by frictional behavior of tire tread that translate driving force, cornering force and braking force between automobile and road as a result of frictional behavior of each tread block. The tire tread block is representative case of rubber block doing frictional behavior. In this paper, frictional behavior of rubber block under compressive force and shear force was analytically obtained by using slip starting position parameter instead of friction coefficient which is uncertain to express exact value between rubber and other surfaces yet. And local coefficients of friction were calculated as a function of compressive force, shear force, shear modulus of rubber, shape factor and slip starting position.

• 한국구조물진단유지관리공학회 논문집
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• 제23권7호
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• pp.152-163
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• 2019

본 연구에서는 강섬유의 혼입, 매트릭스의 압축강도, 전단철근과 전단경간비가 UHPFRC 휨재에 미치는 영향에 대해 총 10개의 실험체에 대한 실험을 통해 검토하였다. 실험결과 2%의 부피비로 강섬유가 혼입된 경우 파괴 패턴을 전단파괴에서 휨파괴로 바꿀 정도로 높은 전단강도 증진효과를 보유하고 있는 것으로 나타났다. 또한 강섬유는 낮은 전단경간비에서 압축스트럿의 파괴를 지연시키는 효과를 가진 것으로 나타났다. 실험 결과 강섬유의 혼입과 전단경간비의 변화에 따라 균열각이 45도보다 낮은 것으로 나타났다. 실험 결과를 UHPC 설계권고안들과 비교해 본 결과 프랑스의 설계권고안은 보수적으로 평가하였고 한국의 설계권고안은 휨 강도에 대해 다소 과대평가하는 것으로 나타났다. 전단강도에 대해서는 두 설계권고안 모두 보수적으로 평가하는 것으로 나타났다.

• Steel and Composite Structures
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• 제42권3호
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• pp.407-426
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• 2022

Superior to traditional welded studs, high strength friction-grip bolted shear connectors facilitate the assembling and demounting of the composite members, which maximizes the potential for efficiency in the construction and retrofitting of new and old structures respectively. Hence, it is necessary to investigate the structural properties of high strength friction-grip bolts used in steel concrete composite beams. By means of push-out tests, an experimental study was conducted on post-installed high strength friction-grip bolts, considering the effects of different bolt size, concrete strength, bolt tensile strength and bolt pretension. The test results showed that bolt shear fracture was the dominant failure mode of all specimens. Based on the load-slip curves, uplifting curves and bolt tensile force curves between the precast concrete slab and steel beam obtained by push-out tests, the anti-slip performance of steel-concrete interface and shear behavior of bolt shank were studied, including the quantitative analysis of anti-slip load, and anti-slip stiffness, frictional coefficient, shear stiffness of bolt shank and ultimate shear capacity. Meanwhile, the interfacial anti-slip stiffness and shear stiffness of bolt shank were defined reasonably. In addition, a total of 56 push-out finite element models verified by the experimental results were also developed, and used to conduct parametric analyses for investigating the shear behavior of high-strength bolted shear connectors in steel-concrete composite beams. Finally, on ground of the test results and finite element simulation analysis, a new design formula for predicting shear capacity was proposed by nonlinear fitting, considering the bolt diameter, concrete strength and bolt tensile strength. Comparison of the calculated value from proposed formula and test results given in the relevant references indicated that the proposed formulas can give a reasonable prediction.

• Steel and Composite Structures
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• 제28권5호
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• pp.527-539
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• 2018

The use of reinforced concrete (RC) shear wall with concrete filled steel tube (CFST) columns and steel fiber reinforced concrete (SFRC) shear wall has aroused widespread attention in recent years. A new shear wall, named SFRC shear wall with CFST columns, is proposed in this paper, which makes use of CFST column and SFRC shear wall. Six SFRC shear wall with CFST columns specimens were tested under cyclic loading. The effects of test parameters including steel fiber volume fraction and concrete strength on the failure mode, strength, ductility, rigidity and dissipated energy of shear wall specimens were investigated. The results showed that all tested shear wall specimens exhibited a distinct shear failure mode. Steel fibers could effectively control the crack width and improve the distribution of cracks. The load carrying and energy dissipation capacities of specimens increased with the increase of steel fiber volume fraction and concrete strength, whilst the ductility of specimens increased with the increase of steel fiber volume fraction and the decrease of concrete strength.

• Advances in concrete construction
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• 제11권2호
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• pp.111-126
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• 2021

Concrete cracking due to brittle tension strength significantly prevents fully utilization of the materials for "flexural-shear failure" type shear walls. Theoretical and experimental studies applying fiber reinforced concrete (FRC) have achieved fruitful results in improving the seismic performance of "flexural-shear failure" reinforced concrete shear walls. To come to an understanding of an optimal design strategy and find common performance prediction method for design methodology in terms to FRC shear walls, seismic performance on shear walls with PVA and steel FRC at edge columns and plastic region are compared in this study. The seismic behavior including damage mode, lateral bearing capacity, deformation capacity, and energy dissipation capacity are analyzed on different fiber reinforcing strategies. The experimental comparison realized that the lateral strength and deformation capacity are significantly improved for the shear walls with PVA and steel FRC in the plastic region and PVA FRC in the edge columns; PVA FRC improves both in tensile crack prevention and shear tolerance while steel FRC shows enhancement mainly in shear resistance. Moreover, the tensile strength of the FRC are suggested to be considered, and the steel bars in the tension edge reaches the ultimate strength for the confinement of the FRC in the yield and maximum lateral bearing capacity prediction comparing with the model specified in provisions.