• Title/Summary/Keyword: Stress Concentration ratio

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Field Test Study on Stress Concentration Ratio of Composited soft ground with Crushed-stone Compaction Pile (쇄석다짐말뚝 복합지반의 응력분담에 관한 현장실험 연구)

  • 김태훈;이민희;최용규
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.717-724
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    • 2003
  • Although sand compaction pile is applied considerably for increase of hearing capacity in domestic, it is getting more necessary to develope the alternative materials because of exhaustion and increase of unit cost of sand. In this study, stress concentration ratio between crushed-stone pile and soft ground was measured and, a displacement ratio 30, 40 and 50%, variation of stress concentration ratio was analyzed. As an increase displacement ratio, the stress concentration effect of crushed-stone compaction pile doesn't increase proportionally and effect of ground improvement in case of ground was good at displacement ratio 30% or 40%. The stress concentration ratio of crushed-stone compaction pile in group piles is 1.5 times that of crushed-stone compaction pile in single pile.

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A Numerical Analysis for the Influential Factors on the Stress Concentration Ratio (모래다짐말뚝지반의 응력분담비에 영향을 미치는 인자에 대한 해석적 연구)

  • Choi, Hyo-Won;Shin, Hyun-Young;Yoo, Han-Kyu;Kim, Soo-Sam
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.966-973
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    • 2005
  • The stress concentration ratio in accordance with area replacement ratios were considered as core elements of design. However, the stress concentration ratio will be vary depends on progress of consolidation in clay ground. And, since it is not sure to know the affecting factors accurately, the value is decided based on field experiences. To use SCP method more effective and correspond to soil improvement, the decision on proper area replacement ratio through the exact stress concentration ratio is very important. Accordingly, a numerical analysis on influence of various factors that needed to make rational designing guide for decision of proper area replacement ratio to stress concentration ratio was executed in this study.

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Stress Concentration Ratio of GCP Depending on the Mixing Ratio of Crushed Stone and Sand (GCP의 쇄석과 모래의 배합비 별 응력분담비)

  • Na, Seung-Ju;Kim, Min-Seok;Park, Kyung-Ho;Kim, Daehyeon
    • Journal of the Korean Geotechnical Society
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    • v.32 no.9
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    • pp.37-50
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    • 2016
  • Gravel compaction pile (GCP) is widely used as it increases the bearing capacity of soft ground and reduces the consolidation settlement. Stress concentration ratio for GCP design is dependent on the area replacement, surcharge pressure and depth. However, a range of stress concentration ratio obtained through field, laboratory experiments and numerical analysis is large. Little study has been done on the stress concentration ratio for the mixing ratio of gravel and sand. The main objective of the study is to evaluate the stress concentration ratio for both area replacement ratio and mixing ratio through literature review and numerical analysis. Numerical analysis using the finite element program ABAQUS 6.12-4 has been performed for the composite ground with GCP. The excess pore water pressure and stress concentration ratio of composite ground have been analyzed for both the area replacement ratio and the mixing ratio. Based on the previous research results, a range of stress concentration ratio obtained from the field tests, laboratory tests, numerical analysis on the GCP studies is found to be 1.7-3.2, 2.0-7.5 and 2.0-6.5, respectively. Based on the numerical analysis results, as the area replacement ratio increases, the stress concentration ratio increases up to 30% and then decreases at 40%. Also, the stress concentration ratio tends to increase up to 70:30 and then to decrease after 60:40.

Centrifugal Model Test on Stress Concentration Behaviors of Composition Ground under Flexible/Stiff Surcharge Loadings (연/강성 하중을 받는 복합지반의 응력분담거동에 대한 원심모형시험)

  • Song, MyungGeun;Bae, WooSeok;Ahn, SangRo;Heo, Yol
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.6
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    • pp.5-15
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    • 2011
  • In this study, centrifuge model tests were performed to investigate stress concentration ratio, stress characteristics of soft clay ground improved by granular compaction piles with changes of piles type, loading condition and area replacement ratio. From the results of rigid loading tests, while vertical stresses acting on clay ground is similar, vertical stresses acting on GCP is larger than those acting on SCP with same replacement ratio. Also, average stress concentration ratio is increased proportionally with increasing the area replacement ratio of GCP and SCP. It was evaluated that average stress concentration ratio of soft clay ground improved by GCP is larger than that of SCP. As a result of flexible loading tests, stress concentration ratio is the highest when replacement ratio of GCP and SCP is 40%. Average stress concentration ratio of soft clay ground improved by GCP is a little more higher than is improved by SCP.

Variation of Stress Concentration Ratio with Area Replacement Ratio for SCP-Reinforced Soils under Quay Wall (치환율에 따른 안벽구조물 하부 SCP 복합지반의 응력분담비)

  • 김윤태
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.16 no.1
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    • pp.18-26
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    • 2004
  • In order to accelerate the rate of consolidation settlement, to reduce settlement, and to increase bearing capacity for soft ground under quay, sand compaction pile method (SCP) has usually been applied. SCP-reinforced ground is composite soil which consists of the sand pile and the surrounding soft soil. One of main important considerations in design and analysis for SCP-reinforced soils is stress concentration ratio according to area replacement ratio. In this paper, the numerical analysis was conducted to investigate characteristics of stress concentration ratio in composite ground. It was found that stress concentration ratio of composite ground is not constant as well as depends on several factors such as area replacement ratio, depth of soft soil, and consolidation process. The values of stress concentration ratio increase during loading stage due to stress transfer of composite soil, and reach up to 2.5∼12 according to area replacement ratio at the end of construction. After the end of consolidation, however, these values are converged to 2.5 to 6.0 irrespective of area replacement ratio due to increase in effective stress of soft soil during consolidation process.

A Study on Stress Analysis of Orthotropic Composite Cylindrical Shells with a Circular or an Elliptical Cutout

  • Ryu, Chung-Hyun;Lee, Young-Shin;Park, Myoung-Hwan;Kim, Young-Wann
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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    • pp.808-813
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    • 2004
  • The stress analysis on orthotropic composite cylindrical shells with one circular or one elliptical cutout subjected to an axial force is carried out by using an analytical and experimental method. The composite cylindrical shell governing equation of the Donnell's type is applied to this study and all results are presented by the stress concentration factor. The stress concentration factor is defined as the ratio of the stress on the region around a cutout to the nominal stress of the shell. The stress concentration factor is classified into the circumferential stress concentration factors and the radial stress concentration factors due to the cylindrical coordinate of which the origin is the center of a cutout. The considered loading condition is only axial tension loading condition. In this study, thus, the maximum stress is induced on perpendicular region against axial direction, on the coordinate. Various cutout sizes are expressed using the radius ratio, (equation omitted), which is the radius of a cutout over one of the cylindrical shell. Experimental results are obtained using strain gages, which are attached around a cutout of the cylindrical shell. As the result from this study, the stress concentration around a cutout can be predicted by using the analytical method for an orthotropic composite cylindrical shell having a circular or an elliptical cutout.

Measurement Conditions of Concrete Pull-off Test in Field from Finite Element Analysis (유한요소 해석을 이용한 현장 콘크리트 부착강도 측정조건)

  • Kim, Seong-Hwan;Jeong, Won-Kyong;Kwon, Hyuck;Kim, Hyoun-Oh;Lee, Bong-Hak
    • Journal of Industrial Technology
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    • v.22 no.A
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    • pp.185-192
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    • 2002
  • The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesive and strength measurement method ignores the effect of stress concentration from shape of specimens. Therefore, this research calculates stress concentration coefficient as the ratio of drilling depth to drilling diameter($h_s/D$), the ratio of overlay thickness to drilling diameter($h_0/D$), the ratio of steel disk thickness to drilling diameter(t/D), the ratio of overlay elastic modulus to substrate modulus($E_1/E_0$), the distance from core to corner border(L_$_{corner}$) and the distance between cores(L_$_{coic}$) vary. The finite element method is adapted to analysis The results from 'the F.E.M analysis are as follows. The stress concentration effects can be minimized when the ratio of drilling depth to drilling diameter($h_s/D$) is 0.20~0.25, the elastic modulus ratio($E_1/E_0$) is 06~1.0, and the ratio of steel disk thickness to drilling diameter(t/D) is 3.0. The overlay thickness, the distance from specimens to corner border(L_$_{corner}$), the distance between cores(L_$_{coic}$) almost do not affect to the stress concentration.

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Stress Analysis of a Discontinuous Composite Using Mechanics of Materials Approach (불연속 복합체의 재료역학적 접근을 통한 응력해석)

  • 김홍건;양성모;노홍길
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.4
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    • pp.63-69
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    • 2003
  • In discontinuous composite mechanics, shear lag theory is one of the most popular model because of its simplicity and accuracy. However, it does not provide sufficiently accurate strengthening predictions in elastic regime then the fiber aspect ratio is small. This is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is a function of several variables, such as the modulus ratio, the fiber volume fraction, the fiber aspect ratio, is proposed. It is found that the modulus ratio($E_f$/$E_m$) is the essential variable among them. Thus, the stress concentration factor is expressed as a function of modulus ratio in the derivation. It is found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the values of interfacial shear stresses and local stress variations in the small fiber aspect ratio regime.

A Study on the Stress Concentration Coefficient due to the Change of Ellipse on a Square Plate (사각 평판에서 타원의 형상 변화에 따른 응력집중계수에 관한 연구)

  • 박정호;김형준;박기훈;조우석;제승봉;김현수
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1434-1437
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    • 2003
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio a/b increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces. As the plate with three holes. the stress $\sigma$$\_$x/ and $\tau$$\_$xy/ of hole 1,3 becomes high, especially $\sigma$$\_$x/ dominant and high.

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A Study on the Stress Concentration Coefficient due to the Change of Position and Shape of Ellipse on a Square Plate (사각 평판에서 타원의 위치와 형상 변화에 따른 응력집중계수의 변화에 관한 연구)

  • 최경호;권영석;박기훈;김현수
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.833-836
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    • 2002
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio ah increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces.

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