• Title/Summary/Keyword: shear design

Search Result 3,122, Processing Time 0.031 seconds

Behavior of Bearing Capacity for Shallow Foundation on a Sand overlying Clay Depending on Bearing Capacity Ratio (점토층 위 모래지반의 지지력비에 따른 얕은 기초의 지지력 거동)

  • Jung, Min Hyung;Shin, Hyo Hee;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.15 no.1
    • /
    • pp.198-208
    • /
    • 2011
  • When a structure which has relatively low load constructs on soft clay, the bearing capacity of the ground will be improved by sand overlying clay. In this condition, verifying the bearing capacity is difficult from the P.B.T etcetera in the in-situ. So, it is needed to estimate precise bearing capacity in the design process. In this study, 2-dimensional chamber tests and FEM analyses are conducted to evaluate behavior of bearing capacity for shallow foundations on a sand overlying clay. Because depth ratio H/B and bearing capacity ratio $q_c/q_s$ are selected as main factors, height of a sand, undrained shear strength of a clay and width of a loading are designated as variables. Results from chamber tests are very similar with those of FEM analyses. And it shows that punching shear mechanism is more suitable than the equation of Okamura et al.(1998). To make continual application of load spread mechanism, the equivalent load spread angle is proposed for H/B and $q_c/q_s$. Also, the linear regression equation of critical depth ratio Hf is suggested for $q_c/q_s$.

Stability Evaluation on Particle Size Characteristics of Bed Materials at High-Velocity Flow (고유속 흐름에서 하상재료의 입도특성에 따른 안정성 평가연구)

  • Kim, Gwang Soo;Jung, Dong Gyu;Kim, Young Do;Park, Yong Sung
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.41 no.4
    • /
    • pp.365-376
    • /
    • 2021
  • In general, domestic streams and rivers are composed of alluvial rivers consisting of sand and gravel beds. These rivers can cause erosion and riverbed changes due to sudden changes in flow rates, such as floods, torrential rains, and heavy rains. In particular, there are various types of erosion, such as contraction erosion caused by changes in river shape, or local erosion occurring around obstacles such as piers, abutments or embankments. In addition, river changes can occur in various forms, such as static or dynamic periods, due to limitations such as flow rate, velocity, and shear stress. This study focused on the erosions of embankments directly related to human casualties among various river structures, and evaluated limit velocities and critical shear stress in order to identify changes in strength of natural materials by identifying the characteristics of natural hoan materials and resistance to erosions. In particular, the limitations of materials according to the type of materials in the river, characteristics of particles, and size of particles were studied using Soil loss, which is a change in the volume of the revetment material, and it is intended to be used as basic data for river design and restoration.

Numerical Analysis on the Turbulence Patterns in The Scour Hole at The Downstream of Bed Protection (하상보호공 직하류부 세굴공의 난류양상에 관한 수치해석적 연구)

  • Lee, Jaelyong;Park, Sung Won;Yeom, Seongil;Ahn, Jungkyu
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.20 no.5
    • /
    • pp.20-26
    • /
    • 2019
  • Where hydraulic structures are to be installed over the entire width of a river or stream, usually a bed protection structure is to be installed. However, a local scour occurs in which the river bed downstream of the river protection system is eroded due to the influence of the upstream flow characteristics. This local scour is dominant in the flow and turbulence characteristics at the boundary of the flow direction and in the material of the bed materials, and may gradually become dangerous over time. Therefore, in this study, we compared the turbulence patterns in the local scour hole at the downstream of the river bed protection with the results of the analysis of the mobile bed experiment, and compared with the application of OpenFoam, a three dimensional numerical analysis model. The distribution of depth-averaged relative turbulence intensities along the flow direction was analyzed. In addition to this result, the stabilization of scour hole was compared with the bed shear stress and Shields parameter, and the results were compared by changing the initial turbulent flow conditions. From the results, it was confirmed that the maximum depth of generation of the three-stage was dominantly developed by the magnitude of depth-averaged relative turbulence intensity rather than the mean flow velocity. This result also suggests that design, construction or gate control are needed to control the depth-averaged relative turbulence intensities in order to reduce or prevent the local scour faults that may occur in the downstream part of the bed protection.

Directional Variation of Apparent Elastic Constants and Associated Constraints on Elastic Constants in Transversely Isotropic Rocks (횡등방성 암석에서 겉보기 탄성정수의 방향성 변화와 탄성정수 제약조건)

  • Youn-Kyou Lee
    • Tunnel and Underground Space
    • /
    • v.33 no.3
    • /
    • pp.150-168
    • /
    • 2023
  • The anisotropic behavior of rocks is primarily attributed to the directional arrangement of rock-forming minerals and the distribution characteristics of microcracks. Notably, sedimentary and metamorphic rocks often exhibit distinct transverse isotropy in terms of their strength and deformation characteristics. Consequently, it is crucial to gain accurate insights into the deformation and failure characteristics of transversely isotropic rocks during rock mechanics design processes. The deformation of such rocks is described by five independent elastic constants, which are determined through laboratory testing. In this study, the characteristics of the directional variation of apparent elastic constants in transversely isotropic rocks were investigated using experimental data reported in the literature. To achieve this, the constitutive equation proposed by Mehrabadi & Cowin was introduced to calculate the apparent elastic constants more efficiently and systematically in a rotated Cartesian coordinate system. Four transversely isotropic rock types from the literature were selected, and the influence of changes in the orientation of the weak plane on the variations of the apparent elastic modulus, apparent shear modulus, and apparent Poisson's ratio was analyzed. Based on the investigation, a new constraint on the elastic constants has been proposed. If the proposed constraint is satisfied, the directional variation of the apparent elastic constants in transversely isotropic rocks aligns with intuitive predictions of their tendencies.

Hybrid Integration of P-Wave Velocity and Resistivity for High-Quality Investigation of In Situ Shear-Wave Velocities at Urban Areas (도심지 지반 전단파속도 탐사를 위한 P-파 속도와 전기비저항의 이종 결합)

  • Joh, Sung-Ho;Kim, Bong-Chan
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.30 no.1C
    • /
    • pp.45-51
    • /
    • 2010
  • In urban area, design and construction of civil engineering structures such as subway tunnel, underground space and deep excavation is impeded by unreliable site investigation. Variety of embedded objects, electric noises and traffic vibrations degrades the quality of site investigation, whatever the site-investigation technique would be. In this research, a preliminary research was performed to develop a dedicated site investigation technique for urban geotechnical sites, which can overcome the limitations of urban sites. HiRAS (Hybrid Integration of Surface Waves and Resistivity) technique which is the first outcome of the preliminary research was proposed in this paper. The technique combines surface wave as well as electrical resistivity. CapSASW method for surface-wave technique and PDC-R technique for electrical resistivity survey were incorporated to develop HiRAS technique. CapSASW method is a good method for evaluating material stiffness and PDC-R technique is a reliable method for determination of underground stratification even in a site with electrical noise. For the inversion analysis of HiRAS techniuqe, a site-specific relationship between stress-wave velocity and resistivity was employed. As for outgrowth of this research, the 2-D distribution of Poisson's ratio could be also determined.

Effects of Functional Improvement of Multiaxis Flat Continuous Soil Cement Earth Retaining Wall (다축 평면 연속형 SCW 흙막이 벽체의 개선 효과)

  • Chung, Choong-Sub;Yoo, Chan Ho;Nam, Ho Seong;Choi, In Gyu;Baek, Seung Cheol
    • Journal of the Korean Geotechnical Society
    • /
    • v.39 no.11
    • /
    • pp.7-22
    • /
    • 2023
  • In January 2022, a new legislation was enforced to enhance the safety of underground construction. Consequently, a comprehensive assessment of underground safety is now an integral part of the planning process, including an evaluation of its impact. Ensuring the stability of temporary retaining walls during underground excavation has become paramount, prompting a heightened focus on the assessment of underground safety. This study delves into the analysis of the Multi-axis Flat Continuous Soil Cement Wall retaining wall (MFS) construction method. This method facilitates the expansion of wall thickness in the ground and provides flexibility in selecting and spacing H-piles. Through laboratory model tests, we scrutinized the load-displacement behavior of the wall, varying the H-pile installation intervals using the MFS method. Additionally, a 3-dimensional numerical analysis was conducted to explore the influence of H-pile installation intervals and sizes on the load for different thicknesses of the MFS retaining wall. The displacement analysis yielded the calculation of the height of the arching effect acting on the wall. To further our understanding, a design method was introduced, quantitatively analyzing the results of axial force and shear force acting on the wall. This involved applying the maximum arching height, calculated by the MFS method, to the existing member force review method. The axial force and shear force, contingent on the H-pile installation interval and size applied to the MFS retaining wall, demonstrated a reduction effect ranging from 24.6% to 62.9%.

Effect Analysis of Tillage Depth on Rotavator Shaft Load Using the Discrete Element Method (이산요소법을 활용한 경심이 로타리 작업기의 경운날 축 부하에 미치는 영향 분석)

  • Bo Min Bae;Dae Wi Jung;Dong Hyung Ryu;Jang Hyeon An;Se O Choi;Yeon Soo Kim;Sang Dae Lee;Seung Je Cho
    • Journal of Drive and Control
    • /
    • v.20 no.4
    • /
    • pp.115-122
    • /
    • 2023
  • This study utilized a discrete element method (DEM) simulation, as one of the virtual field trials, to predict the impact of tillage depth on the rotary blade shaft during rotavator tilling. The virtual field for the simulation was generated according to soil properties observed in an actual field. Following the generation of particles for the virtual field, a sequence of calibration steps followed to align the mechanical properties more closely with those of real soil. Calibration was conducted with a focus on bulk density and shear torque, resulting in calibration errors of just 0.02% for bulk density and 0.52% for shear torque. The prediction of the load on a rotary tiller's blade shaft involved a three-pronged approach, considering shaft torque, draft force, and vertical force. In terms of shaft torque, the values exhibited significant increases of 42.34% and 36.91% for every 5-centimeter increment in tillage depth. Similarly, the vertical force saw substantial growth by 40.41% and 36.08% for every 5-centimeter increment. In contrast, the variation in draft force based on tillage depth was comparatively lower at 18.49% and 0.96%, indicating that the effect of tillage depth on draft force was less pronounced than its impact on shaft torque and vertical force. From a perspective of agricultural machinery research, this study provides valuable insights into the DEM soil modeling process, accounting for changes in soil properties with varying tillage depths. These findings are expected to be instrumental in future agricultural machinery design studies.

Evaluation of the applicability of the surface wave method to rock fill dams (사력댐에서의 표면파 기법 적용성 평가 연구)

  • Kim, Jong-Tae;Kim, Dong-Soo;Park, Heon-Joon;Bang, Eun-Seok;Kim, Sung-Woo
    • Geophysics and Geophysical Exploration
    • /
    • v.13 no.1
    • /
    • pp.9-23
    • /
    • 2010
  • In current design practice, the shear wave velocity (Vs) of the core and rock-fill zone of a dam, one of the characteristics essential for seismic response design, is seldom determined by field tests. This is because the borehole seismic method is often restricted in application, due to stabilisation activities and concern for the security of the dam structure, and surface wave methods are limited by unfavourable in-situ site conditions. Consequently, seismic response design for a dam may be performed using Vs values that are assumed, or empirically determined. To estimate Vs for the core and rock-fill zone, and to find a reliable method for measuring Vs, seismic surface wave methods have been applied on the crest and sloping surface of the existing 'M' dam. Numerical analysis was also performed to verify the applicability of the surface wave method to a rock-fill dam. Through this numerical analysis and comparison with other test results, the applicability of the surface wave method to rock-fill dams was verified.

Design and Experimental Verification of Uni-Injector Using Gas Methane and Lox as Propellants (가스메탄/액체산소를 추진제로 하는 단일 인젝터 설계 및 실험적 검증)

  • Jeon, Jun Su;Min, Ji Hong;Jang, Ji Hun;Ko, Young Sung;Kim, Sun Jin
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.37 no.3
    • /
    • pp.275-283
    • /
    • 2013
  • An injector that uses methane gas ($CH_4$) and liquid oxygen ($LO_x$) as propellants was designed to verify the combustion characteristics of an engine that uses methane, which is one of the next-generation propellants. A swirl/shear coaxial-type injector was used, and flow analysis was performed using Fluent to determine the main design parameters of the injector. A hydraulic test was performed to understand the atomization and spray pattern characteristics of the injector. Next, a combustion test was performed at the design point to understand the ignition and combustion stability. Additional combustion tests were performed according to the O/F ratio to investigate the combustion characteristics and stabilities using the characteristic exhaust velocity ($C^*$) and fluctuation of the chamber pressure. The experimental results showed that the combustion efficiency was greater than 90%, and the pressure fluctuation was lower than 2% under all conditions.

Damping Ratios for Seismic Design of SC Structures (SC구조의 내진설계를 위한 감쇠비)

  • Lee, Seung-Joon;Kim, Won-Ki
    • Journal of Korean Society of Steel Construction
    • /
    • v.22 no.5
    • /
    • pp.487-496
    • /
    • 2010
  • The structural damping ratios for seismic design of nuclear power plant structures are specified in Regulatory guide 1.61 of the United States NRC for RC structures of 4%(OBE) and 7%(SSE), and for steel structures of 3%(OBE) and 4%(SSE), but not for steel-plate concrete (SC) structures that have been developed recently. The objective of this study is to investigate the damping ratios of SC structures by identifying the relative differences in the damping ratios between RC and SC structures. An experimental study was performed on four specimens, RC-S, RC-M, SC-S and SC-M, where S stands for shear-governed and M for moment-governed. The conducted method was free vibration testing by rupturing a brittle steel plate that linked the actuator and the mass center. The test results were analyzed to determine fundamental frequencies and damping ratios at various load levels. By examining the relative differences in damping ratios of four specimens, it is proposed for SC structures to use the same damping ratio of 4% as RC one at OBE, but 1% less damping ratio than RC one resulting in 6% at SSE.