• Title/Summary/Keyword: shear friction test

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Evaluation of Dowel Bar on the One-way Shear and Shear Friction Behaviors of Hybrid Beams Composed of Steel and Reinforced Concrete Elements (강재-콘크리트 하이브리드 보의 일축 전단 및 전단마찰 거동에서 장부철근의 영향평가)

  • Kwon, Hyuck-Jin;Yang, Keun-Hyeok;Hong, Seung-Hyun
    • Journal of the Korea Concrete Institute
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    • v.29 no.1
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    • pp.93-100
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    • 2017
  • This study examined the one-way shear in concrete beam region and shear friction in joint region of a hybrid H-steel-reinforced concrete (HSRC) beam system with a simple ductile connection. One-way shear tests were conducted under overhanging beam system with a shear span-to-depth ratio of 1.6. Simple beams for shear friction were tested under two-point symmetrical top loads producing a clear shear span-to-depth ratio of 0.1. Test results showed that the dowel bars arranged in joint region insignificantly influence the propagation of shear cracks but enhances the shear strength of the HSRC beams by approximately 25%. The one-way shear strength and shear friction strength of HSRC beams can be conservatively evaluated using the design equations specified in ACI 318-14 and EC2 shear provisions.

An experimental study on shear mechanical properties of clay-concrete interface with different roughness of contact surface

  • Yang, Wendong;Wang, Ling;Guo, Jingjing;Chen, Xuguang
    • Geomechanics and Engineering
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    • v.23 no.1
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    • pp.39-50
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    • 2020
  • In order to understand the shear mechanical properties of the interface between clay and structure and better serve the practical engineering projects, it is critical to conduct shear tests on the clay-structure interface. In this work, the direct shear test of clay-concrete slab with different joint roughness coefficient (JRC) of the interface and different normal stress is performed in the laboratory. Our experimental results show that (1) shear strength of the interface between clay and structure is greatly affected by the change of normal stress under the same condition of JRC and shear stress of the interface gradually increases with increasing normal stress; (2) there is a critical value JRCcr in the roughness coefficient of the interface; (3) the relationship between shear strength and normal stress can be described by the Mohr Coulomb failure criterion, and the cohesion and friction angle of the interface under different roughness conditions can be calculated accordingly. We find that there also exists a critical value JRCcr for cohesion and the cohesion of the interface increases first and then decreases as JRC increases. Moreover, the friction angle of the interface fluctuates with the change of JRC and it is always smaller than the internal friction angle of clay used in this experiment; (4) the failure type of the interface of the clay-concrete slab is type I sliding failure and does not change with varying JRC when the normal stress is small enough. When the normal stress increases to a certain extent, the failure type of the interface will gradually change from shear failure to type II sliding failure with the increment of JRC.

Sensitivity of Dimensional Changes to Interfacial Friction over the Definite Range of Friction Factor in Ring Compression Test (링 압축시험에서 마찰인자 구간별 치수 변화의 민감도)

  • Lim, J.Y.;Noh, J.H.;Hwang, B.B.
    • Transactions of Materials Processing
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    • v.19 no.8
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    • pp.494-501
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    • 2010
  • The main objective of this study is to examine the sensitivity of calibration curves of FEA of ring compression test to frictional shear factor. Ring compression test has been investigated by measuring dimensional changes at different positions of ring specimen and they include the changes in internal diameter at the middle and top section of the specimen, outer diameter at the middle and top section, surface expansion at the top surface, respectively. Initial ring geometries employed in analysis maintain a fixed ratio of 6 : 3 : 2, i.e. outer diameter : inner diameter : thickness of the ring specimen, which is generally known as 'standard' specimen. A rigid plastic material for different work-hardening characteristics has been modeled for simulations using rigid-plastic finite element code. Analyses have been performed within a definite range of friction as well as over whole range of friction to show different sensitivities to the interfacial friction for different ranges of friction. The results of investigation in this study have been summarized in terms of a dimensionless gradient. It has been known from the results that the dimensional changes at different positions of ring specimen show different linearity and sensitivity to the frictional condition on the contact surface.

Vane Shear Test on Nakdong River Sand (베인 전단시험기를 이용한 낙동강모래의 마찰각에 관한 연구)

  • Park, Sung-Sik;Zhou, An;Kim, Dong-Rak
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.3
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    • pp.463-470
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    • 2016
  • A vane shear test (VST) is a simple testing method for determining an undrained shear strength of cohesive soils by minimizing soil disturbance. In this study, the VST was used to determine a shear strength of sand. Dry Nakdong River sand was prepared for loose and dense conditions in a cell and then pressurized with 25, 50, 75 or 100 kPa from the surface of sand. A vane (5 cm in diameter and 10 cm in height) was rotated and a torque was measured within sand. When a torque moment by vane and friction resistance moment by sand is assumed to be equalized, a friction angle can be obtained. When a vane rotates within clay, a uniform undrained shear strength is assumed to be acting on cylindrical failure surface. On the other hand, when it is applied for sand, the failure shape can be assumed to be an octagonal or square column. The relationship between measured torque and resistant force along assumed failure shapes due to friction of sand was derived and the internal friction angle of sand was determined for loose and dense conditions. For the same soil condition, a series of direct shear test was carried out and compared with VST result. The friction angle from VST was between 24-42 degrees for loose sand and 33-53 degrees for dense sand. This is similar to those of direct shear tests.

A Study on the Estimation and Application of Failure Coefficients of Rock (암석의 파괴조건계수 평가 및 적용성에 관한 연구)

  • 장명환;양형식
    • Geotechnical Engineering
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    • v.14 no.4
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    • pp.103-116
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    • 1998
  • To estimate pure shear strength, 150 sets of triaxial test data were analyzed. The proportional coefficient of shear strength($I_c$) at zero normal stress was nonlinearly decreased as failure coefficient m increases, while the internal friction $\phi_0$ at zero normal stress was nonlinearly increased. The ratio of shear strength $(c/\phi_0)$was inversely proportional to the ratio of the internal friction angles$(\phi/phi_0)$ The shear strength decreased as m increased, while internal friction angle increased. And uniaxial strength was proportional to $c,\phi$ Regression analysis showed that shear strength strongly affects m and $\sigma_c$ The proportional coefficient of shear strength was nonlinearly increased with RMR, while the internal friction angle $(\phi}$was linearly decreased.

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Using grain size to predict engineering properties of natural sands in Pakistan

  • Aziz, Mubashir
    • Geomechanics and Engineering
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    • v.22 no.2
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    • pp.165-171
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    • 2020
  • Laboratory determination of strength and deformation behavior of clean sands and gravels has always been challenging due to the difficulty in obtaining their undisturbed samples. An alternative solution to this problem is to develop correlations between mechanical properties of cohesionless soils and their gradation characteristics. This study presents database of 3 natural sands with 11 varying particle size gradation curves to allow investigating relationships between mean particle size, maximum and minimum void ratio, relative density and shear strength of the test soils. Direct shear tests were performed at relative densities of 50, 75 and 95% to explore the effects of gradation and density on the angle of internal friction of the modeled sand samples. It is found that the mean grain size D50 bears good correlations with void ratio range (emax - emin) and peak angle of internal friction 𝜙'peak. The generated regression models are in good agreement with published literature and can be considered as reliable for natural sands in Pakistan. These empirical correlations can save considerable time and efforts involved in laboratory and field testing.

A Study of Characteristic of Friction Angles between Sand and Artificial Rock Interface by Direct Shear Test (직접전단시험에 의한 모래와 인공암석 경계면의 마찰각 특성 연구)

  • Yang, Hong-Suk;Lee, Byok-Kyu;Jang, Seung-Jin;Lee, Su-Gon
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.8
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    • pp.65-73
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    • 2012
  • Soil-rock interface, mainly founded in Granite region of Korea, is known as one of the important factor of the slope failure at the rainfall due to smaller shear strength than soil itself. However, research of the effect on slope stability by soil-rock interfaces is insufficient. Therefore, a series of direct shear tests were performed in order to investigate the effect of soil-rock interface on slope stability. The method of tests is to get sand itself and sand-artificial rock interface shear strength from different grain size of sands and artificial rock samples. The results of tests show that the friction angle of interface depends primarily on particle size and surface roughness. Interface friction angle ratio ${\mu}(={\delta}/{\Phi})$ is in the range of 0.75 ~ 0.96, this results indicate that interface friction angle is smaller than sand itself.

Friction behavior of controlled low strength material-soil interface

  • Han, WooJin;Kim, Sang Yeob;Lee, Jong-Sub;Byun, Yong-Hoon
    • Geomechanics and Engineering
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    • v.18 no.4
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    • pp.407-415
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    • 2019
  • A controlled low strength material (CLSM) is a highly flowable cementitious material used for trench backfilling. However, when applying vertical loads to backfilled trenches, shear failure or differential settlement may occur at the interface between the CLSM and natural soil. Hence, this study aims to evaluate the characteristics of the interface friction between the CLSM and soils based on curing time, gradation, and normal stress. The CLSM is composed of fly ash, calcium sulfoaluminate cement, sand, silt, water, and an accelerator. To investigate the engineering properties of the CLSM, flow and unconfined compressive strength tests are carried out. Poorly graded and well-graded sands are selected as the in-situ soil adjacent to the CLSM. The direct shear tests of the CLSM and soils are carried out under three normal stresses for four different curing times. The test results show that the shear strengths obtained within 1 day are higher than those obtained after 1 day. As the curing time increases, the maximum dilation of the poorly graded sand-CLSM specimens under lower normal stresses also generally increases. The maximum contraction increases with increasing normal stress, but it decreases with increasing curing time. The shear strengths of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. Moreover, the friction angle for the CLSM-soil interface decreases with increasing curing time, and the friction angles of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. The results suggest that the CLSM may be effectively used for trench backfilling owing to a better understanding of the interface shear strength and behavior between the CLSM and soils.

Scale Effects of the Specimen on Shear Strength of sand by Direct Shear Test (직접전단시험에 의한 모래의 전단강도에서 시편의 크기효과)

  • Kim, Joon-Seok;Kim, Ji-Hyun
    • Journal of the Society of Disaster Information
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    • v.15 no.4
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    • pp.590-596
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    • 2019
  • Purpose: An experimental study was conducted on the sand samples for the size effect of the test specimens, one of the problems of the direct shear test. Method: Jumunjin standard sand, a representative sand of Korea, was used as sand sample. The large direct shear test was performed to analyze the shear strength at 50%, 60%, 70%, and 80% relative density, and then the comparative results were compared with the test results of the small direct shear test. Result: It was analyzed that the internal friction angle of the small shear tester tended to be relatively large in the dense region. It was analyzed that the results of the large shear tester tend to be relatively large in the region of medium relative density. Conclusion: The size effect on the samples in the direct shear test on sandy soil was analyzed to be relatively small.