• International Journal of Automotive Technology
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• v.8 no.4
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• pp.483-491
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• 2007

A closed form solution of a composite mechanics system is performed for the investigation of elastic-plastic behavior in order to predict fiber stresses, fiber/matrix interfacial shear stresses, and matrix yielding behavior in short fiber reinforced metal matrix composites. The model is based on a theoretical development that considers the stress concentration between fiber ends and the propagation of matrix plasticity and is compared with the results of a conventional shear lag model as well as a modified shear lag model. For the region of matrix plasticity, slip mechanisms between the fiber and matrix which normally occur at the interface are taken into account for the derivation. Results of predicted stresses for the small-scale yielding as well as the large-scale yielding in the matrix are compared with other theories. The effects of fiber aspect ratio are also evaluated for the internal elastic-plastic stress field. It is found that the incorporation of strong fibers results in substantial improvements in composite strength relative to the fiber/matrix interfacial shear stresses, but can produce earlier matrix yielding because of intensified stress concentration effects. It is also found that the present model can be applied to investigate the stress transfer mechanism between the elastic fiber and the elastic-plastic matrix, such as in short fiber reinforced metal matrix composites.

• Tunnel and Underground Space
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• v.27 no.2
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• pp.89-99
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• 2017

For a successful performance of Carbon Capture Sequestration (CCS) projects, appropriate injection conditions should be designed to be optimized for site specific geological conditions. In this study, we built a simple 2-dimensional analysis model, based on the geology of Jang-gi basin which is one of the potential sites of domestic CCS projects. We evaluated the impact of initial stress conditions and injection rate through coupled TOUGH-FLAC simulator. From the preliminary analysis, we constructed risk scenarios with the higher potential of shear slip and performed scenario analysis. Our analysis showed that normal stress regime produced the highest potential of shear slip and stepwise increasing injection rate scenario resulted in much larger pore pressure build up and consequent higher potential of the shear slip, which was evaluated using a mobilized friction coefficient.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.4
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• pp.245-275
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• 2017

The present investigation deals, Dufour and heat source effects on radiative MHD slip flow of a viscous fluid in a parallel porous plate channel in presence of chemical reaction. The non-linear coupled partial differential equations are solved by using two term perturbation technique subject to physically appropriate boundary conditions. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall. It is observed that the effect of Dufour and heat source parameters decreases the velocity and temperature profiles.

• Computers and Concrete
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• v.24 no.2
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• pp.173-183
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• 2019

This study presents experimental and numerical results of prestressed concrete composite beams with different casting and stressing sequence. The beams were tested under three-point bending and it was found that prestressed concrete composite beams could not achieve monolith behavior due to interface slippage between two layers. The initial stress distribution due to different construction sequence has little effect on the maximum load of composite beams. The multi-step FE analyses could simulate different casting and stressing sequence thus correctly capturing the initial stress distribution induced by staged construction. Three contact algorithms were considered for interaction between concrete layers in the FE models namely tie constraint, cohesive contact and surface-to-surface contact. It was found that both cohesive contact and surface-to-surface contact could simulate the interface slip even though each algorithm considers different shear transfer mechanism. The use of surface-to-surface contact for beams with more than 2 layers of concrete is not recommended as it underestimates the maximum load in this study.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.27-34
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• 2010

A finite element analysis has been conducted to clarify the behaviour of a single pile in heaving ground related to ground excavation. The numerical analysis has included soil slip at the pile-soil interface, analysing the interaction between the pile and the clay has been studied. The study includes the upward movement of the pile, the relative shear displacement between the pile and the soil and the shear stresses at the interface and the axial force on the pile. In particular, the shear stress transfer mechanism at the pile-soil interface related to a decrease in the vertical soil stress has been rigorously analysed. Due to the reductions in the vertical soil stress after excavation, the relative shear displacement and the shear stress along the pile have been changed. Upward shear stress developed at most part of the pile (Z/L=0.0-0.8), while downward shear stress is mobilized near the pile tip (Z/L=0.8-1.0) resulting in tensile force on the pile, where Z is the pile location and L is the pile length. Some insights into the pile behaviour in heaving ground analysed from the numerical analyses has been reported.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.27-40
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• 1999

In limit equilibrium methods(LEM), all methods employ the same definition of the safety factor as a ratio of the shear strength of the soil to the shear stress required for equilibrium, employing certain assumptions with regard to equilibrium. In addition, in the conventional finite element method of analysis, the minimum safety factor is obtained assuming certain slip surfaces after the state of stress are found. Although the stress states are obtained from the finite element method(FEM), the slope stability analysis follows the conventional method that assumes a potential slip surface. In this study, a slope stability analysis based on FEM is developed to locate the slip surface by tracking the weakest points in the slope based on the local safety factor considering the magnitude and direction of the shear stresses. It has also been applied to be compared with the slip surfaces predicted by LEM. A computer program has been developed to draw contour lines of the local safety factors automatically. This method is illustrated through a simple hypothetical slope, a natural soil slope, and a dam slope. The developed method matches very well with the conventional LEM methods, with slightly lower global safety factors.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.747-757
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• 2004

With steel and concrete composite beams, the incomplete interaction between the steel and the concrete slab leads to an appreciable increase in beam deflections. Moreover, encased composite beams using a deep deck plate or hollow-core PC slabs are critical to deflection due to their inherent geometry. In this paper, by using the calculation tools that were developed for a previous study on the deflection of encased composite beams considering the slip effects and load-slip curve, the shear bond stress and additional deflection induced due to interface slip of the encased composite beam are presented. It was found that the slip effects significantly contribute to the encased composite beam deflections and result in stiffness reduction of up to 30% compared to that of full shear interaction beams. The predicted results were compared with the measurement of 18 specimens tested in this study, and comparisons show a high degree of accuracy, within 6%.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.5-19
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• 2018

The characteristics of the skin shear stress distribution for the fixed length of the ground anchor are extremely nonlinear and the engineering mechanisms are complex relatively. So it is difficult to design the anchors simulating the actual behavior by considering various soil conditions and nonlinear behavior. Due to these limits, constant skin shear stress distributions for the whole fixed length of the ground anchor are usually assumed in the design for the sake of convenience. In this study, to assess the pull-out behavior of the tension-type ground anchors, the in-situ pull-out tests in weathered-soil conditions were carried out. Based on the test results, the skin shear behaviors for the fixed length of tension-type ground anchors were established and the multi-linear slip shear model predicting this behavior and an analytical technique applying this model were proposed. From the similarity between the results of the in-situ pull-out tests and those of the analytical technique, the applicability and availability of the multi-linear slip shear model and the proposed analytical technique were verified. The maximum shear stress was developed at the start point of the fixed length acting with the smaller load than the maximum pull-out load but the minimum shear stress was developed at the start point of the fixed length and the maximum shear stress was developed at the point apart from the start point of the fixed length after the maximum pull-out load.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.54-60
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• 2013

In this study, a finite element model based on the SU/PG scheme was developed to solve shallow-water equations and the influences of parameters and internal boundary conditions on depth-averaged flow behavior were investigated. To analyze the effect of roughness coefficient and eddy viscosity on flow characteristics, the developed model was applied to rectangular meandering channel with two bends, and transverse velocities and water depth distributions were examined. As the roughness coefficient adjacent to wall increased, the velocities near the wall decreased, and the reduced velocities were compensated by the expanding mid-channel velocities. In addition, the flow characteristics around a circular cylinder were analyzed by varying the internal boundary conditions as free slip and no slip. The assignment of slip condition changed the velocity distribution on the cylinder surface and reduced the magnitude of the shear stress up to one third.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.233-240
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• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.