• Structural Engineering and Mechanics
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• 제47권4호
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• pp.531-544
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• 2013

Compared with pavement structures of ordinary road sections, pavement structures in the intersection are exposed to more complex traffic characteristics which may exacerbates pavement distresses such as fatigue-cracking, shoving, shear deformation and rutting. Based on a field survey about traffic characteristics in the intersection conducted in Shanghai China, a three dimensional dynamic finite-element model was developed for evaluating the mechanistic responses in the pavement structures under different traffic characteristics, namely uniform speed, acceleration and deceleration. The results from this study indicated that : (1) traffic characteristics have significant effects on the distributions of the maximum principal strain (MPS) and the maximum shear stress (MSS) at the pavement surface; (2) vehicle acceleration or deceleration substantially impact the MPS and MSS at pavement surface and could increase the magnitude of them by 20 percent to 260 percent; (3) in the vertical direction, with the increase of vehicle deceleration rate, the location of the MPS peak value and the MSS peak value changes from the sub-surface layer to the pavement surface.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.839-842
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• 2008

현행 기준식에서는 철근콘크리트 보의 취성적 전단 파괴를 방지하기 위하여 전단보강철근이 항복한 이후에 복부 콘크리트가 압축파괴하도록 최대전단철근비에 대한 제한을 두고 있다. 최대전단철근비에 대한 제한은 각 기준식마다 매우 상이하다. ACI 318-05, CSA-04 와 EC2-02기준에서는 최대전단철근비가 콘크리트의 압축강도에 따라서 변화하지만, 일본기준식은 압축강도와 무관하게 일정한 값이다. 고강도콘크리트가 사용될 경우에 CSA-04와 EC2-02기준에서 요구하는 최대전단철근비는 ACI 318-05의 두 배 이상으로 기준식마다 상이하게 최대전단철근비를 제한하고 있다. 이 연구에서는 10개의 철근콘크리트 보 실험을 통하여 최대철근비가 미치는 보의 거동 및 내력을 평가하였다. 실험 결과에 의하면 ACI 318-05에서 요구하는 철근비보다 많은 전단보강철근이 배근된 보에서도 전단보강철근이 항복한 이후에 콘크리트가 압축파괴하였다.

• 한국정밀공학회지
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• 제6권4호
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• pp.94-102
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• 1989

The effect of plastic strain on the surface integrity of mild steel (SS 41) was studied. This paper shows that the recrystallization technique is adequate to evaluate the plastic strain in a machined surface experimentally. The relations between the plastic strain and the machining conditions are quantitatively evaluated by using the recrystallization technique. The obtained results are summarized as follows. 1. The surface integrity of steel is considerably influenced by the amount of surface region deformation produced by changes in cutting conditions. 2. The plastic strain in machined surface produced by changes of the cutting conditions is evaluated by the recyrstallization technique. 3. The plastic strain increases with the increase of depth of cut and the decrease of rake angle. 4. When the cutting force is high and the rake angle is small, the value of maximum true strain reaches to high. 5. The maximum true strain is related to the cutting energy, and the values increase with the increase of the unit shear and total engergy in constant depth with the increase of the energy values.

• 한국농공학회지
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• 제43권5호
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• pp.132-144
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• 2001

Iln order to figure out criteria of bentonite for using as impervious material of waste landfill, laboratory experiments were performed to reveal the geotechnical properties of soil-bentonite mixtures such as compaction test, direct shear test, unconfined compression test, triaxial compression test, consolidation test and permeability test. The results of the study are summarized as follows ; 1. Based on the compaction test, optimum moisture content increased with the increase of bentonite content, but maximum dry density decreased. 2. In unconfined compression test, the maximum strength of the soil-bentonite mixtures appeared at 10% bentonite content. The correlation equation between stress($\sigma$) and strain($\varepsilon$) of the soil-bentonite mixtures is given by ; $\sigma=\frac{a\cdot\varepsilon}{\varepsilon^n+b}$ 3. In shear test of the mixtures. the shear strength showed an increasing trend with increase of bentonite content and the maximum shear strength appeared at 10% bentonite content. 4. In consolidation test, the coefficient of compressibility $(a_v)$$(m_v)$$(C_v)$

• Geomechanics and Engineering
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• 제19권5호
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• pp.435-445
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• 2019

A series of element tests with different drainage conditions and strain rates were performed on compacted unsaturated non-plastic silt in unconfined conditions. Soil samples were compacted at water contents from dry to wet of optimum with the degree of saturation varying from 24 to 59.5% while maintaining the degree of compaction at 80%. The tests performed were shear infiltration tests in which specimens had constant net confining pressure, pore air pressure was kept drained and constant, just before the shear process pore water pressure was increased (and kept constant afterwards) to decrease matric suction and to start water infiltration. In constant water content tests, specimens had constant net confining pressure, pore air pressure was kept drained and constant whereas pore water pressure was kept undrained. As a result, the matric suction varied with increase in axial strain throughout the shearing process. In both cases, maximum shear strength was obtained for specimens prepared on dry side of optimum moisture content. Moreover, the gradient of stress path was not affected under different strain rates whereas the intercept of failure was changed due to the drainage conditions implied in this study.

• 콘크리트학회논문집
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• 제26권2호
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• pp.159-169
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• 2014

이 연구에서는 철근콘크리트 전단벽의 횡하중 거동과 연성을 합리적으로 평가하기 위해서 모멘트-곡률관계를 정립하고 이로부터 단순화된 횡하중-횡변위관계를 제시하였다. 최초 휨 균열, 인장철근 항복, 최대내력, 최대내력의 80% 및 인장철근파단시점에서 모멘트와 곡률은 힘의 평형조건과 변형적합조건으로부터 정립되었다. 최대내력 이후의 곡률평가를 위한 압축측연단 콘크리트 변형률은 Razvi and Saatcioglu의 구속된 콘크리트의 응력-변형률 관계를 이용하여 최대응력의 감소계수와 횡보강근 체적지수의 함수로 제시하였다. 모멘트 평가모델은 변수연구를 통하여 인장철근지수, 수직철근지수 및 축력지수의 함수로 일반화하였다. 횡변위는 전단벽의 높이에 따라 분포된 이상화된 곡률로부터 모멘트 면적법을 이용하여 환산하였다. 제시된 횡하중-횡변위관계는 기존 실험 결과와 잘 일치하였으며, 특히 최대내력 이후의 거동을 잘 평가하였다.

• 한국재료학회지
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• 제28권2호
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• pp.113-117
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• 2018

Effects of annealing temperature on the microstructure and mechanical properties through thickness of a cold-rolled Cu-3.0Ni-0.7Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5h at $200{\sim}900^{\circ}C$. The microstructure of the copper alloy after annealing was different in thickness direction depending on an amount of the shear and compressive strain introduced by rolling; the recrystallization occurred first in surface regions shear-deformed largely. The hardness distribution of the specimens annealed at $500{\sim}700^{\circ}C$ was not uniform in thickness direction due to partial recrystallization. This ununiformity of hardness corresponded well with an amount of shear strain in thickness direction. The average hardness and ultimate tensile strength showed the maximum values of 250Hv and 450MPa in specimen annealed at $400^{\circ}C$, respectively. It is considered that the complex mode of strain introduced by rolling effected directly on the microstructure and the mechanical properties of the annealed specimens.

• 한국농공학회지
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• 제36권3호
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• pp.90-99
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• 1994

To investigate the undrained shear strength characteristics of marine soils with high water content, high compressibility and weak bearing capacity, a series of undrained triaxial tests with pore pressure measurements on undisturbed and disturbed Banwol marine clay in normally consolidated and overconsolidated states is carried out. The results and main conclusions of this study are summarized as follows : 1 . When the consolidation pressure is increased, the maximum deviator stress of disturbed and undistubed clay in normally consolidated state is increased. Pore pressure parameters and internal friction angle of undisturbed clay are greater than those of disturbed clay. 2. The relationship between pore pressure and axial strain of undisturbed clay in normally consolidated state can be expressed as a hyperbolic function like stress-strain relation proposed by Kondner. 3. In the pore pressure-axial strain relation of disturbed clay in normally consolidated state, failure ratio R'f is greatly deviated in the range of 0.7~0.9 proposed by Christian and Desai. 4. For overconsolided clay, when overconsolidation ratio (OCR) is increased, normalized maximum deviator stress is increased and maximum pore pressure is decreased gradually. 5. Cohesion of overconsolidated clay is greater than that of nomally consolidated clay and internal friction angle slightly is decreased. 6. Pore pressure parameter at failure (Af) of overconsolidated clay is varied with OCR, Af becomes negative values with increment in OCR

• Geomechanics and Engineering
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• 제11권5호
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• pp.713-723
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• 2016

Shear wave velocities of three selected sandy soils subject to drained triaxial compression test were continuously measured using the bender elements. The shear wave velocity during isotropic compression, as widely recognized, increased as confining pressure increased and they were correlated well. However, during drained shearing, the mean effective stress could no further provide a suitable correlation. The shear wave velocity during this stage was almost constant with respect to the mean effective stress. The vertical stress was found to be more favorable at this stage (since confining stress was kept constant). When sample was attained its peak stress, the shear wave velocity reduced and deviated from the previously existed trend line. This was probably caused by the non-uniformity induced by the formation of shear band. Subsequently, void ratios computed based on external measurements could not provide reasonable fitting to the initial stage of post-peak shear wave velocity. At very large strain levels after shear band formation, the digital images revealed that sample may internally re-arrange itself to be in a more uniform loose stage. This final stage void ratio estimated based on the proposed correlation derived during pre-peak state was close to the value of the maximum void ratio.

• 한국지반공학회논문집
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• 제19권2호
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• pp.189-197
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• 2003

본 논문은 공진주시험과 삼축압축시험을 이용하여 소변형률(0.0001%~l%) 범위에서 섬유혼합토의 변형 특성을 규명하였으며, 최대전단탄성계수를 잣대로 보강효과를 평가하였다. 또한 단섬유의 직경에 대한 길이의 비(형상비), 흙의 중량에 대한 섬유 중량의 섬유혼합비, 단섬유의 종류에 따른 보강효과를 비교 검토하였다. 시료는 주문진 표준사에 폴리프로필렌 재질의 단섬유를 무작위로 배합하여 사용하였다. 섬유혼합토의 최대전단탄성계수는 비혼합토에 비해 최대 30%까지 증가하였고, 비선형 영역에서의 전단탄성계수 감소량도 억제되었다. 형상비가 증가할수록 최대전단 탄성계수는 증가하고, 단사에 비해 망사의 보강 효과가 큰 것으로 나타났다. 섬유혼합비는 0.3 % 부근에서 보강효과가 가장 커, 최적인 것으로 확인되었다.