• Title/Summary/Keyword: Effective Shear Stress

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Design Method of RC Flat Plate Slab Considering Unbalanced Moment (불균형모멘트를 고려한 RC 무량판 슬래브 설계방법)

  • Song, Jin-Kyu;Sing, Ho-Beom;Oh, Sang-Won;Han, Sun-Ae
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.149-152
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    • 2008
  • In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress of direct shear occurred by balanced gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. For this problem, a model to show unbalanced moment-punching shear interrelation was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment-punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, a effective width enlargement factor for deciding the unbalanced moment strength of flat plates with shear reinforcements was proposed. The interrelation model proposed in this paper is very effective for the design because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.

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Effect of Average and Cyclic Shear Stress on Undrained Cyclic Behavior of Marine Silty Sand (해양 실트질 모래의 비배수 동적 거동에 대한 평균 및 반복전단응력의 영향)

  • Muhammad, Safdar;Son, Su-Won;Kim, Jin-Man
    • Journal of the Korean Geotechnical Society
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    • v.30 no.1
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    • pp.17-25
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    • 2014
  • Offshore wind turbine foundations are subjected to wind, current and wave loadings. Hence, both static and cyclic behaviors of foundation's soil are important for the design of offshore wind turbine foundation. Undrained cyclic behaviors of soils depend upon the number of loading cycles, vertical effective stress, cyclic shear strain, relative density, and the combination of cyclic and average shear stresses. In order to evaluate the effect of average and cyclic shear stresses on the undrained cyclic behavior of marine silty sand, cyclic direct simple shear (CDSS) tests are performed with relative density of 85%, vertical effective stress of 200 and 300 kPa, and failure criteria of either 15% double amplitude cyclic shear strain (${\gamma}_{cyc}$) or permanent shear strain (${\gamma}_{p}$). The results are presented in the form of design graphs or contour diagrams. The undrained cyclic behavior of marine silty sand is found to be dependent on cyclic and average shear stresses and/or the combination of both shear stresses. It is found that when significant average shear stress exists the permanent or progressive shear strain is the govering failure criteria instead of cyclic shear strain.

Feasibility study on the Evaluation of the degree of consolidation using shear waves for soft clay deposits (전단파를 이용한 연약지반의 압밀도 평가기법 적용성 연구)

  • Youn, Jun-Ung;Kim, Jong-Tae;Lee, Jin-Sun;Kim, Dong-Soo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.442-451
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    • 2008
  • The evaluation of field degree of consolidation on soft clays has been an important problem in geotechnical areas. Monitoring either settlements or pore water pressures has been widely applied in the filed, but occasionally they have some problems. This study addresses the suggestion and application of another method for evaluating the degree of consolidation using shear wave velocities. A research site where soft clay layers were consolidated by surcharging loads was chosen. Laboratory tests were performed to determine the relation between shear wave velocity and effective stress. Field seismic tests were conducted several times during the consolidation of the clay layers. The tests results show that the shear wave velocity increased significantly as clays consolidated. The shear wave velocities at each field stress states were derived from the laboratory results and the degree of consolidation was evaluated by comparing the shear wave velocities obtained by laboratory and field seismic methods. In most stress states, the degree of consolidation evaluated using the shear wave velocity matched well with that obtained from field settlement record, showing the potential of applying the method using shear waves in the evaluation of field degree of consolidation on soft clay deposits.

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Study on the Time Dependent Stress-Strain Behavior of Clay (점성토의 시간의존적 응력 - 변형 특성에 관한 연구)

  • 지인택;강우묵
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.30 no.4
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    • pp.134-153
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    • 1988
  • This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

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Embankment and Excavation Behaviour with Shear Parameters of Soft Clayey Soil in FEM (점성토의 유한요소해석에서 전단파라미터에 따른 성토 및 굴착 거동)

  • Kim, Byung Il;Choi, Chanyong;Hong, Kang Han;Han, Sang Jae
    • Journal of the Korean Geotechnical Society
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    • v.34 no.2
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    • pp.5-17
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    • 2018
  • In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

Characteristics of Undrained Shear Strength of Yangsan Clay (양산지역 점토의 비배수 전단강도 특성)

  • 김길수;임형덕;이우진
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.71-78
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    • 2000
  • SHANSEP method involves the consolidation to stresses in excess of the preconsolidation pressure in order to overcome sample disturbance effect. The concept of SHANSEP is based on an approach to laboratory test which attempts to reproduce the in-situ conditions more closely than is possible in routine tests and evaluates normalized strength parameters for the soil as a function of OCR. But SHANSEP method can be applied only to fairly uniform clay deposits, and is unsuitable for a random deposit. In this study, CK/sub o/U triaxial compression test and incremental loading consolidation test were performed for the application of SHANSEP method on Yangsan clay. During the K/sub o/-consolidation, triaxial specimens were consolidated to stress equal to two times the in-situ vertical effective stress. And for overconsolidated condition, the specimens were swelled to a known vertical effective stress in order to have the desired OCR. With the results of CK/sub o/U triaxial compression test using the block samples, the relationship between c/sub u//σ/sub vc/' and OCR on Yangsan clay was established. For evaluating the undrained shear strength of Yangsan clay with depth, CK/sub o/U triaxial compression test was performed using the piston samples taken from Yangsan site. And also undrained shear strength was analyzed from the in-situ test such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that of CK/sub o/U triaxial compression test.

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Application of Bender Elements in Consolidation, Tomography, and Liquefaction Tests (압밀, 토모그래피, 액상화시험에서 벤더엘리먼트의 적용)

  • Lee, Jong-Sub;Lee, Chang-Ho
    • Journal of the Korean Geotechnical Society
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    • v.22 no.8
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    • pp.43-54
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    • 2006
  • The scope of this paper covers the applications of bender element tests in consolidation, tomography, and liquefaction. Loading and unloading time during consolidation are evaluated based on shear wave velocity. As S-wave velocity is dependent on effective stress, the loading step may be determined. However, cautions are required due to the different mechanism between the settlement and effective stress criteria. The stress history may be evaluated because the S-wave shows the cement controlled regime and stress controlled regimes. A fixed frame complemented with bender elements permits S-wave tomography The tomography system is tested at low confinement within a true triaxial cell. Results show that shear wave velocity tomography permits monitoring changes in the velocity field which is related to the average effective stress. To monitor the liquefaction phenomenon, S-wave trans-illumination is implemented with a high repetition rate to provide detailed information on the evolution of shear stiffness during liquefaction. The evolution of shear wave propagation velocity and attenuation parallel the time-history of excess pore pressure during liquefaction. Applications discussed in this paper show that bender elements can be a very effective tool for the detection of shear waves in the laboratory.

Effective Longitudinal Shear Modulus of Polymeric Composite Using Iosipescu Shear Test (Iosipescu Shear Test를 이용한 고분자 복합재료의 종방향 전단계수 연구)

  • Jeong, Tae-Heon;Kwon, Yong-Su;Lee, You-Tae;Lee, Dong-Joo
    • Journal of the Korean Society of Industry Convergence
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    • v.3 no.1
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    • pp.61-67
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    • 2000
  • Effective shear modulus of continuous fiber reinforced polymeric composites is measured using a modified Iosipescu Shear Test(IST) and compared with data obtained by finite element analyses that a concept of unit cell is. It is found that the numerical results of the longitudinal shear modulus give a good agreement with experimental data at lower fiber volume fraction. In this paper, both the distance and stress transfer between the fibers are discussed as the major factors.

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On the effect of GFRP fibers on retrofitting steel shear walls with low yield stress

  • Edalati, S.A.;Yadollahi, Y.;Pakar, I.;Bayat, M.
    • Earthquakes and Structures
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    • v.8 no.6
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    • pp.1453-1461
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    • 2015
  • In this article the non-linear behavior of the shear wall with low yield stress retrofitted with Glass Fiber Reinforced Polymer (GFRP) is investigated under pushover loading. The models used in this study are in ${\frac{1}{2}}$ scale of one story frame and simple steel plates with low yield stress filled the frame span. The models used were simulated and analyzed using finite elements method based on experimental data. After verification of the experimental model, various parameters of the model including the number of GFRP layers, fibers positioning in one or two sides of the wall, GFRP angles in respect to the wall and thickness of the steel plate were studied. The results have shown that adding the GFRP layers, the ultimate shear capacity is increased and the amount of energy absorbed is decreased. Besides, the results showed that using these fibers in low-thickness plates is effective and if the positioning angle of the fibers on the wall is diagonal, its behavior will improve.

A Basic Study on Torsion Shear Tests in Soils (흙의 비틀림전단시험에 관한 기초적 연구)

  • 홍원표
    • Geotechnical Engineering
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    • v.4 no.1
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    • pp.17-28
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    • 1988
  • Among several types of element tests to predict soil behalf.iota in a laboratory, the torsion shear apparatus, in which the directions of principal stresses could be rotated during shearing, wra explained. In this study, this torsion shear apparatus was improved so as to be used in tests on clay specimens . And some undrained torsion shear tests u.ere performed on remolded specimens of Ko-consolidated clay to investigate the influence of reorientation of the principal stress directions on the stress-strain behavior The soil behavior by the torsion shear apparatus without torque was compared It.ith that by the conventional triaxial compression tests . The stress path, provided by both vertical loads and torque during torsion shear tests, has much effect on the stress-strain behavior, the pore pressure and the effective principal stress ratio . The rotation angle of the principal stress and the b-value were gradually increased with increasing shear strain, but converged to the values at failure.

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