• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.327-338
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• 2006

Friction type high tension bolted joints is one of the most common steel structure connections and requires significant concerns on axial force of the bolts. However, its high shear capacity is not appropriately considered in design and hence the number of bolts is over-designed than actually required. It is primarily due to a slip-load-based design method. This study, therefore, suggests a new technology of connection using a shear ring, which may reduce the shortcomings from the friction-typed high tension bolted joints and maximize the advantages from the bearing-typed joints. Experimental and numerical studies were performed to compare the capacity of the suggested method with traditional high tension bolted joints. From the results, it is known that the suggested connections has higher bearing capacity than friction-typed high tension bolted joints due to the higher shear resistance from the ring. For further study, it may be necessary to investigate on design parameters including the depth of shear ring, for increased connection capacity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.181-194
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• 2013

Landslides are known as gravitational mass movements that can carry the flow materials ranging in size from clay to boulders. The various types of landslides are differentiated by rate and depositional features. Indeed, flow characteristics are observed from very slow-moving landslides (e.g., mud slide and mud flow) to very fast-moving landslides (e.g., debris avalanches and debris flows). From a geomechanical point of view, shear-rate-dependent shear strength should be examined in landslides. This paper presents the design of advanced ring-shear apparatus to measure the undrained shear strength of debris flow materials in Korea. As updated from conventional ring-shear apparatus, this apparatus can evaluate the shear strength under different conditions of saturation, drainage and consolidation. We also briefly discussed on the ring shear apparatus for enforcing sealing and rotation control. For the materials with sands and gravels, an undrained ring-shear test was carried out simulating the undrained loading process that takes place in the pre-existing slip surface. We have observed typical evolution of shear strength that found in the literature. This paper presents the research background and expected results from the ring-shear apparatus. At high shear speed, a temporary liquefaction and grain-crushing occurred in the sliding zone may take an important role in the long-runout landslide motion. Strength in rheology can be also determined in post-failure dynamics using ring-shear apparatus and be utilized in debris flow mobility.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1129-1134
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• 2007

Payload fairing protects satellites and electrical equipments from the external environment. Payload fairing is jettisoned before satellite separation. Assembly frame for the separation of payload fairing were assembled with shear bolts. The role of shear bolts is to support structural load during flight and they are cut by explosion of pyro. The assembly frame which is connected by shear bolts is separated after the cutting of shear bolts. In this paper, structural tests and analysis were done for the design of the shear bolt. Compression, bending and shear load apply to the hardware including assembly frame. Test results showed that design of the shear bolt satisfied both structural strength for the support of flight load and required low strength for the cutting of shear bolts.

• Food Science of Animal Resources
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• v.24 no.1
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• pp.23-28
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• 2004

The objective of this study was to reduce the tumbling time with improved binding capacity for the manufacture of restructured hams(RHs) using a transglutaminase(TGase). The RHs had 73.9∼75.7% moisture, 3.63∼4.18% fat, 16.6∼20.6% protein with pH values of 5.95∼6.10 and water activity of 0.95∼0.96. No differences in hunter color values or functional properties were observed with the addition of 0.3% TGase or increased tumbling time. However, RHs without TGase had lower(p<0.05) textural profile analysis(TPA) values than those with TGase, regardless of tumbling time. Improved shear values were also observed with increased tumbling time only in RHs without TGase or with the addition of 0.3% TGase as well. This study indicated that 1 hr tumbling with the addition of 0.3% TGase improved the textural characteristics, as compared to the control 1(1 hr tumbling without TGase), resulting in similar shear values of the treatment, which tumbled for 4 hrs without TGase.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.5-15
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• 2014

Abandoned mine deposits are exposed to various physico-chemical geo-environmental hazards and disasters, such as acid mine drainage, water contamination, erosion, and landslides. This paper presents the ring shear characteristics of waste materials. The ring shear box with a rotatable O-ring was used in this study. Three tests were performed: (i) Shear stress-time relationship for given normal stress and shear speed, (ii) shear stress as a function of shear speed, and (iii) shear stress as a function of normal stress. For a given normal stress (50 kPa) and speed (0.1 mm/sec), the materials tested exhibit a strain softening behavior, regardless of drainage condition. The peak and residual shear stresses were determined for each normal stress and shear speed. The shear stress was measured when shear speed is equal to 0.01, 0.1, 1, 10, 50, 100 mm/sec or when normal stress is equal to 20, 40, 60, 80, 100, 150 kPa. From the test results, we found that the shear stress increases with increasing shear speed. The shear stress also increases with increasing normal stress. However, different types of shearing mode were observed in drained and undrained conditions. Under drained condition, particle crushing was observed from the shearing zone to the bottom of lower ring. Under undrained condition, particle crushing was observed only at the shearing zone, which has approximately 1 cm thick. It means that a significant high shear speed under undrained condition can result in increased landslide hazard.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.176-176
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• 2011

환형수조는 점착성 퇴적물의 이송특성 연구를 위해 가장 선호되는 실험 장치로 알려져 있다. 과거 많은 연구자들은 퇴적물의 이송특성, 특히 침식/퇴적 특성 조사를 위해 주로 수로를 이용한 실험적 연구를 수행하였는데, 최초의 실험적 연구들은 주로 직선수조에서 수행되었다. 그러나 입자간의 응집이 중요한 역할을 하는 점착성 퇴적물의 경우에, 직선수조 끝단에서의 자유낙하 및 재순환 펌프의 날개에 의해 응집된 토사가 쉽게 분리될 수 있어 그 타당성이 의문시 되어 왔으며, 이러한 단점을 보완하기 위해 환형수조가 고안되었다. 환형수조는 수면과 접하여 회전하는 상부링의 마찰력에 의해 흐름이 생성되기 때문에 시간의 제약 없이 흐름조건을 동일하게 만들 수 있다는 큰 장점을 갖는다. 그러나 환형수조는 원주유속의 속도차이 및 원심력으로 인한 2차 순환류를 형성시켜 반경 방향(radial direction)에서의 바닥전단응력을 불균일하게 하는 단점을 갖는다. 이러한 2차 순환류와 바닥전단응력의 불균일을 저감시키기 위하여 환형수조의 몸체를 상부링의 회전 방향과 역방향으로 직접 회전시키는 방법이 채택되어져 왔다. 한편, 환형수조의 상부링과 몸체를 서로 역방향으로 동시에 회전시키는 양방향 회전(counter-rotation)의 적용을 위해서는 2차 순환류가 최소가 되며 바닥전단응력이 균일해지는 최적 회전속도비에 대한 분석은 필수적 사항이다. 이를 위하여, 상부링과 몸체의 회전속도에 따라 변화하는 수조내부의 흐름특성 및 평균바닥전단응력에 대한 연구가 선행되어야만 한다. 이에 본 연구에서는 전산유체역학을 이용하여 전북대에 설치된 환형수조의 상부링과 몸체의 회전속도에 따라 변화하는 수조내부에서의 흐름특성 및 바닥전단응력에 대한 분석이 수행되었다. 또한, 이를 기초로, 환형수조의 최적 회전속도비 산출을 위한 연구가 수행 중에 있다. 이러한 결과들은 추후 환형수조를 이용한 점착성 퇴적물의 침식/퇴적 등과 같은 이송특성 연구시, 퇴적물에 작용하는 흐름조건의 정밀산정을 위한 기초자료로 활용될 수 있을 것이다.

• Journal of the Korean Geotechnical Society
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• v.37 no.5
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• pp.5-17
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• 2021

In this study, the shear behavior between pile-sandy soil interface was quantified based on series of rigorous ring shear test results. Ring shearing test was carried out to observe the shear behavior prior to failure and behavior at residual state between most commonly used pile materials - steel and concrete - and Jumunjin sand. The test was set to clarify the shear behavior under various confinement conditions and soil densities. The test results were converted in to representative friction angles for various test materials. Additional numerical analysis was executed to validate the accuracy of the test results. Based on the test results and the numerical validation, it was found that due to the dilative and contractive nature of sand, its interface behavior can be categorized in to two different types : soils with higher densities tend to show peak shear stress and moves on to residual state, while on the other hand, soils with lower densities tend to show bilinear load-transfer curves along the interface. However, the relative density and the confining stress was found to affect the friction angle only in the small train range, and converges as it progresses to large deformation. This study established a large deformation analysis method which can successfully simulate and predict the large deformation behavior such as ring shear tests. Moreover, the friction angle derived from the ring shear test result and verified by numerical analysis can be applied to numerical analysis and actual design of various pile foundations.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.463-471
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• 2016

A shear strength model for the high-shear ring anchor consisting of a steel ring and a rod was developed based on the shear tests on single high-shear ring anchors. The shear strength was found to be proportional to $f_{ck}{^{0.75}}$ which is a similar characteristic to the strength of shear connectors used in composite structures. The effects of the compressive strength of concrete, edge distance, and embedment length of rod are included in the proposed model. Comparison with 22 tests shows that the average and the coefficient of variation of test-to-prediction ratios are 1.01 and 7.57%, respectively. Push tests on the specimens having four high-shear ring anchors at each face were conducted and the measured shear strengths were compared with the predictions by the proposed model. For the specimen with an edge distance of 100 mm, a splitting failure occurred and for the specimens with an edge distance of 150 mm, a failure mode mixed with splitting and bearing occurred, which were very similar to the failures of shear tests on single high-shear ring anchors. In case of a splitting failure, the overlap of failure surfaces could be prevented by providing the longitudinal spacing of 400 mm which is four times of the edge distance. In case of a bearing failure, the failure area is less than 150 mm from the center of the anchor and therefore the overlap of failure surfaces could be prevented by providing the longitudinal spacing of 200 mm. The average of the test-to-prediction ratios of Push tests is 98%, which means that the proposed mode can be applied to predict the shear strength of the multiple high-shear rings.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.21-26
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• 2020

Natural soil is composed of particles of various sizes, and the shear behavior which is a kind of mechanical behavior of the soil is affected by the particle size distribution. In addition, since the natural soil contains a large mixture of coarse and fine grained soil, it is difficult to clearly understand the shear behavior of the soil. Therefore, a ring shear test was conducted on sandy soils that has various particle size distribution in order to identify the effect of the distribution on shear characteristics of soils. At this time, sand and silt were used for coarse and fine grained soils, respectively, to make sandy soils by changing the silt content. Also the water was supplied during the test to confirm shear characteristics of sandy soils with various particle size distributions. The result shows that the shear strength increases as the silt content increases, and the strength decreases as the silt content increases over the sand. Besides, residual shear strength gradually decreases because of the silt content when the water is supplied.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.1-12
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• 2011

In order to analyze the influence of particle bonding and crushing on the characteristics of shear behavior, especially residual shear behavior of granular soil, ring shear test was simulated by using DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Total four models including two non-crushing models and two crushing models were created in this study by using clump or cluster model built in PFC. The applicability of Lobo-crushing model proposed by Lobo-Guerrero and Vallejo(2005) was investigated. In addition, the results of ring shear test were analyzed and compared with those of direct shear test. The results showed that the modelling of ring shear test should be conducted to investigate the residual shear behavior. The Lobo-crushing model cannot be applied to investigate the residual shear strength. Finally, it can be concluded that the numerical models excluding Lobo-crushing model suggested in this study can be used extensively for other studies concerning the residual shear behavior of granular soil including soil crushing.