• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.214-219
• /
• 2004

Crack tip behavior of single mode loading condition(mode I)depend on tensile loading component but one of mixed mode loading condition(mode I+II) have influenced on shear loading component like the practical structure. Because crack closure is caused by shear loading component under mixed-mode loading a research on the behavior in the stage of crack initiation and propagation require to be evaluate about crack closure effect by fatigue crack surface friction. For that reasion we examined the behavior at the crack tip by direct measuring method. Measured behavior at the crack tip was analyzed through vector crack tip displacement. As a result, crack propafation equation was corrected by considering with crack closure effect. In addition we compared fatigue fracture crack surface and crack closure level.

• 한국강구조학회 논문집
• /
• 제26권1호
• /
• pp.11-20
• /
• 2014

2001년 이후 앵커의 설계는 Concrete Capacity Design(CCD) 방법이 적용되고 있는데, 국내 기준에서는 지진하중에 대한 콘크리트의 파열파괴강도를 정적 파괴강도의 75%로 제한하고 있다. 본 연구에서는 무근콘크리트에 매입된 선설치앵커의 동적 전단하중에 대한 콘크리트 파열파괴강도 평가하기 위한 실험을 수행하였다. 이를 위해 직경 20 mm의 앵커에 대해 정적 하중과 동적 편진하중에 대한 실험을 각각 3개의 시험체에 대해 수행하였으며, 앵커의 연단거리는 120 mm를 적용하였다. 동적 실험은 15 cycle의 편진하중을 1 Hz의 속도로 재하하였으며 반복하중단계의 크기를 키워가면서 최종 파괴 시까지 가력하였다. 실험으로부터 동적 전단하중에 의한 콘크리트 파열파괴강도는 정적하중에 의한 것과 거의 같은 파괴강도를 보였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.898-905
• /
• 2005

The settlement of embankment on soft clay includes shear settlement due to shear deformation. Even though the consolidation settlement is not related to lateral displacement, but shear settlement makes the embankment unstable because it deforms ground and decreases the ground strength. In order to determine the shear deformation behaviour during embankment construction, 3 cases (1B, 2B, and 3B) of rapid undrained loading tests on soft clays were performed. Shear settlement is consist of elastic settlement, plastic settlement and viscous settlement. Elastic settlement isn't considered because the range is small, therefore the first is the range of plastic displacement, and the second is that of viscous displacement in the displacement-time curve for each loading stage. After determining that the change in the inclination of the viscous displacement range is larger than in the plastic displacement range after the ground failure occurs for the loading stage, the stability management methods were suggested considering that it is hard to divide the plastic displacement range and the viscous displacement range. The stability management method was based on the ratio of the plastic displacement range's inclination and the viscous displacement range's inclination. A stability management method based on the ratio of the total inclination for each loading stage compared to the whole inclination in the initial loading stage was also recommended.

• Geomechanics and Engineering
• /
• 제17권4호
• /
• pp.333-342
• /
• 2019

Geological dynamic hazards during coal mining can be caused by the failure of a composite system consisting of roof rock and coal layers, subject to different loading rates due to different advancing velocities in the working face. In this paper, the uniaxial compression test simulations on the composite rock-coal layers were performed using $PFC^{2D}$ software and especially the effects of loading rate on the stress-strain behavior, strength characteristics and crack nucleation, propagation and coalescence in a composite layer were analyzed. In addition, considering the composite layer, the mechanisms for the advanced bore decompression in coal to prevent the geological dynamic hazards at a rapid advancing velocity of working face were explored. The uniaxial compressive strength and peak strain are found to increase with the increase of loading rate. After post-peak point, the stress-strain curve shows a steep stepped drop at a low loading rate, while the stress-strain curve exhibits a slowly progressive decrease at a high loading rate. The cracking mainly occurs within coal, and no apparent cracking is observed for rock. While at a high loading rate, the rock near the bedding plane is damaged by rapid crack propagation in coal. The cracking pattern is not a single shear zone, but exhibits as two simultaneously propagating shear zones in a "X" shape. Following this, the coal breaks into many pieces and the fragment size and number increase with loading rate. Whereas a low loading rate promotes the development of tensile crack, the failure pattern shows a V-shaped hybrid shear and tensile failure. The shear failure becomes dominant with an increasing loading rate. Meanwhile, with the increase of loading rate, the width of the main shear failure zone increases. Moreover, the advanced bore decompression changes the physical property and energy accumulation conditions of the composite layer, which increases the strain energy dissipation, and the occurrence possibility of geological dynamic hazards is reduced at a rapid advancing velocity of working face.

• Geomechanics and Engineering
• /
• 제17권6호
• /
• pp.553-564
• /
• 2019

This paper presents experimental results of rock-concrete bi-material discs under cyclically diametrical compression. It was found that both specimens under cyclical and static loading failed in three typical modes: shear crack, tensile crack and a combined mode of shear and wing crack. The failure modes transited gradually from the shear crack to the tensile one by increasing the interface angle between the interface and the loading direction. The cycle number and peak load increased by increasing the interface angle. The number of cycles and peak load increased with the interface groove depth and groove width, however, decreased with increase in interface groove spacing. The concrete strength can contribute more to the cycle number and peak load for specimens with a higher interface angle. Compared with the discs under static loading, the cyclically loaded discs had a lower peak load but a larger deformation. Finally, the effects of interface angle, interface asperity and concrete strength on the fatigue strength were also discussed.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2001년도 춘계학술대회 논문집
• /
• pp.249-256
• /
• 2001

This study investigated the shear stiffness of level of small strain with time effect. Time effect consists of rest time, loading rate of recent and current stress path. In addition, for the measurement of small strain, overconsolidated state was represented in a triaxial cell, and drained stress path tests were carried out. Test results show that the loading rate of recent stress path has no effects on the stiffness of very small strain, but the shear stiffness of level of small strain increases with it. Finally, the rest time and the loading rate of current stress path have the effects on the shear stiffness of initial and small strain.

• Structural Engineering and Mechanics
• /
• 제17권1호
• /
• pp.69-85
• /
• 2004

The novel form of composite walling system consists of two skins of profiled steel sheeting with an in-fill of concrete. Such walling system can be used as shear elements in steel framed building subjected to lateral load. This paper presents the results of small-scale model tests on composite wall and its components manufactured from very thin sheeting and micro-concrete tested under monotonic and cyclic shear loading conditions. The heavily instrumented small-scale tests provided information on the load-deformation response, strength, stiffness, strain condition, sheet-concrete interaction and failure modes. Analytical models for shear strength and stiffness are derived with some modification factor to take into account the effect of quasi-static cycling loading. The performance of design equations is validated through experimental results.

• Steel and Composite Structures
• /
• 제2권1호
• /
• pp.51-66
• /
• 2002

Perforated shear connectors currently used in composite steel and concrete structures are described and evaluated. Modifications of the perforated connector suitable for common use injavascript:confirm_mark('abe', '1'); civil and bridge engineering are proposed. The connectors were tested in laboratories of CTU Prague for shear load capacity. Push tests of connectors with 32 mm openings and with 60 mm openings, both in normal and lightweight concrete of different strength characteristics and with different transverse reinforcement, were carried out. The experimental study also dealt with the connector height and parallel arrangement of two connectors and their influence on shear resistance. While extensive tests with static loading were carried out, fatigue tests under repeated loading are still in progress. After statistical evaluation of the experimental results and comparisons with other available data the authors developed reasonable shear resistance formulas for all proposed arrangements.

• Earthquakes and Structures
• /
• 제9권4호
• /
• pp.767-788
• /
• 2015

A steel shear wall with double-tapered links and in-plane reference was developed for assisting the assessment of the structural condition of a building after an earthquake while maintaining the original role of the wall as a passive damper device. The double-tapered link subjected to in-plane shear deformation is designed to deform torsionally after the onset of local buckling and works as an indicator of the maximum shear deformation sustained by the shear wall during an earthquake. This paper first examines the effectiveness of double-tapered links in the assessment of the structural condition under various types of loading. A design procedure using a baseline incremental two-cycle loading protocol is verified numerically and experimentally. Meanwhile, in-plane reference links are introduced to double-tapered links and greatly enhance objectivity in the inspection of notable torsional deformation with the naked eye. Finally, a double-layer system, which consists of a layer with double-tapered links and a layer with rectangular links made of low-yield-point steel, is tested to demonstrate the feasibility of realizing both structural condition assessment and enhanced energy dissipation.

• 터널과지하공간
• /
• 제10권1호
• /
• pp.45-58
• /
• 2000

다양한 하중 조건하의 암석 절리에 대한 수리적 거동을 규명하기 위해서 수리전단 시험이 가능한 주기 전단시험 시스템을 설계, 제작하였다. 실험실에서 인공 절리 시료에 대한 압축,전단 조건하의 수리 시험을 실시하였다. 시험 전의 시료에 대한 3차원 간극 측정을 통해 절리의 간극 분포 특성을 규명하였다. 수직응력에 따른 투수계수 변화는 기존 수리 모델과 잘 일치하였다. 전단 하중하의 수리적 거동은 초기에는 팽창 특성을 따랐으며, 팽창의 증가에 따라 투수계수가 커겼다. 전단이 진행됨에 따라 유동률은 충전물 생성과 간극의 엇갈림으로 인해 다소 일정해졌다. 주기전단 하의 수리 거동 역시 돌출부 손상과 충전물 생성의 영향을 받았다. 또한 압축과 전단 하중하의 수리 간극과 역학 간극의 관계가 조사, 비교되었다.