• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.386-393
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• 2013

In this study, the so-called repeated plate load bearing test (RPBT) used to get $E_{v2}$ values in order to check the degree of compaction of subgrade, and to get design parameters for determining the thickness of the trackbed foundation, is investigated. The test procedure of the RPBT method is scrutinized in detail. $E_{v2}$ values obtained from the field were verified in order to check the reliability of the test data. The $E_{v2}$ values obtained from high-speed rail construction sites were compared to converted modulus values obtained from resonant column (RC) test results. For these tests, medium-size samples composed of the same soils from the field were used after analyzing stress and strain levels existing in the soil below the repeated loading plates. Finite element analyses, using the PLAXIS and ABAQUS programs, were performed in order to investigate the impact of the strain influence coefficient. This was done by getting newly computed $I_z$ to get the precise strain level predicted on the subgrade surface in the full track structure; under wheel loading. It was verified that it is necessary to use precise loading steps to construct nonlinear load-settlement curves from RPBT in order to get correct $E_{v2}$ values at the proper strain levels.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.2
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• pp.105-116
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• 2010

The estimation of surface settlement, ground behavior and tunnel displacement are the main factors in urban tunnel design with shallow depth and unconsolidated soil. On deformation analysis of shallow tunnel, it is important to identify possible deformation mechanism of shear bands developing from tunnel shoulder to the ground surface. This paper investigated the effects of key design parameter affecting deformation behavior by numerical analysis using nonlinear model incorporating the reduction of shear stiffness and strength parameters with the increment of the maximum shear strain after the initiation of plastic yielding. Numerical parametric studies are carried out to consider the reduction of shear stiffness and strength parameters, horizontal stress ratio, cohesion and shotcrete thickness.

• Geotechnical Engineering
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• v.13 no.4
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• pp.177-198
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• 1997

Since decomposed granite soil shows various characteristics of shear behavior dependent on initial conditions such as weathering degree and grain breakage, it is nacessary to invert ligate stress -strain relationship and changes of shear characteristics for different initial conditions. Associated with abovefnentioned view, direct shear tests, and triaxial compression tutsts(Ef, CD) were carried out in this study for undisturbed and disturbed compacted weathered granite samples obtained from 4 construction work sites with the various weathering degree and components of parent rocks. The deformation behavior of undisturbed samples under small confining stress shows hardening to softening, which is similar to that of over nsolidated clay whereas disturbed weathered granite soils do hardeningfonstant regardless of weathering degree, which is also similar to sedimentary clay. Conventional direct shear-tests for undisturbed samples show a tendency to overestimate cohesion. It is possidle to approximate stress ratio(q/p') and volumetric increment ratio(dv/ds) in the triaxital compression tests by an equation, ($dv/d\varepsilon,=\alpha(M-\eta))$ irrespective of moisture content, weathering degree and disturbance.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.135-140
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• 2004

Wear mechanisms may be briefly classified by mechanical, chemical and thermal wear. A plane strain finite element method is used with a new material stress and temperature fields to simulate orthogonal machining with continuous chip formation. Deformation of the workpiece material is healed as elastic-viscoplastic with isotropic strain hardening and the numerical solution accounts for coupling between plastic deformation and the temperature field, including treatment of temperature-dependent material properties. Effect of the uncertainty in the constitutive model on the distributions of strait stress and temperature around the shear zone are presented, and the model is validated by comparing average values of the predicted stress, strain, and temperature at the shear zone with experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.173-185
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• 1988

This study is intended to investigate the shear fatigue behaviour of reinforced concrete beams based on a series of experiments, and verify the test results in comparison with the analysis result obtained by using a nonlinear finite element method. The experiments are divided into the tests under the static loading and the test under the dynamic fatigue loading. In order to investigate the shear failure behaviour under static loadings, four specimens for three different cases were made and tested. The behaviour of stirrups with the static stress and strain variations were observed based on the results of these tests. In the fatigue fracture tests, eleven specimens for four different cases were made and tested. Various observations on mid-span deflection of test beams and tensile strains of reinforcing steels as well as stirrups were made against various fatigue loadings. It may be concluded that the shear fatigue strengths of R.C. specimens at one million cycles turn out to be approximately 65 percent of the static ultimate shear strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.67-75
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• 2013

The flow stress of zircaloy-4 used in the spacer grid supporting a nuclear fuel rod was determined by the Johnson-Cook model, and model parameters were determined using reverse engineering. Parameters such as A, B, n and $\dot{\varepsilon}_0$ were determined by the tensile test result. To obtain the parameters C and m, a slot milling test and numerical simulation were performed. The objective functions were defined as the difference between the experimental and the simulation results, and then, the parameters were determined by minimizing the objective function. To verify the validity of the determined parameters, cross-verification for each case was conducted through a shearing test and simulation. The results tend to show agreement with the experimental results, such as the features of sheared edges and maximum punch force, with the correlation coefficients exceeding at least 0.97.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.5-12
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• 2010

In this study, in order to clarify the effect of the direction of cyclic shear on the post-earthquake settlement the multi-directional shear tests were carried out for Toyoura Japan standard sand, Genkai natural sand, Kaolinite and the Granulated Blast Furnace Slag (GBFS). The diameter and the height of the specimen are 75 mm and 20 mm, respectively. In a series of tests, the number of strain cycles was adjusted as n=5, 20, 30, 100, 200 and the shear strain amplitudes were varied from 0.1% to 1.0%. The relative densities of each samples were also adjusted as Dr=50, 60 and 70%. From the test results for Toyoura sand and GBFS, it is clarified that the post-earthquake settlement is relatively large at the small relative density and becomes large with the shear strain amplitude. When the influence of difference on the direction of cyclic shear decreases, the post-earthquake settlement strain for Toyoura sand is converged to a constant value, but the GBFS increases with the number of strain cycles. In addition, the post-earthquake settlement is in the order of Kaolinite > Toyoura sand > Genkai sand > GBFS.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.4
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• pp.13-20
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• 2024

In this study, when subjected to in-plane shear such as a shear wall, the behavior characteristics of a concrete member using CFRP rebars were investigated when the longitudinal reinforcement ratio was kept constant at 2.96% and the transverse reinforcement ratio was changed from 0.30 to 2.98%. The evaluation was conducted based on MCFT theory and analyzed by comparison with the case of concrete members using steel rebars. When the reinforcement ratio ranged from 0.30 to 1.19%, concrete members employing CFRP rebars exhibited higher shear strength compared to those using steel rebars. In contrast, at high reinforcement ratios of 1.79 and 2.98%, it was observed that the shear strength of the member with CFRP rebar was lower compared to the member with steel rebar. Maximum shear strain was observed to be higher for members reinforced with steel rebars at lower reinforcing bar ratios, while for ratios of 0.97% and above, CFRP rebars resulted in higher maximum shear strain. As the reinforcement ratio increases, the use of CFRP rebar instead of steel rebar results in a greater increase in maximum shear strain. By analyzing the difference in strain in the reinforcing bar as well as the difference in principal strain in the element caused by differences in the mechanical properties of the steel rebar and CFRP rebar, the shear strength and shear strain when using steel rebar and CFRP rebar with different reinforcement ratios can be compared and analyzed.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.39-47
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• 2005

Fiber reinforced soils have recently implemented to fills and base layers of highways and railroads, and deformation behaviors of reinforced soils in turn should be investigated. The paper evaluated deformation characteristics of fiber reinforced sands and their effectiveness of reinforcement using resonant column tests. The specimens were prepared by varying gradation and mixing polypropylene staple fibers of 0.3% fiber content. Maximum shear moduli of reinforced sands were increased by up to 30% with increasing uniformity coefficient. Shear moduli of well-graded reinforced sands were larger than those of poorly-graded ones regardless of confining pressure in the whole range of shearing strain and reinforcement was, in turn, more effective with higher uniformity coefficient.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.567-573
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• 2017

The drive shaft of passenger vehicle has an important role in transmitting the torque between the power train system and the wheels. Torsional fatigue failures occur generally in the connection parts of the spline edge of the drive shaft, when there is significant fatigue damage under repeated twisting loads. A heat treatment, an induction hardening process, has been adopted to increase the torsional strength as well as the fatigue life of the drive shaft. However, it is still unclear how the extension of the induction hardening process in a used material relates to its shear-strain fatigue life range. In this study, a shear-strain controlled torsional-fatigue test with a specially designed specimen was conducted by an electro-dynamic torsional fatigue test machine. A finite element analysis of the drive shaft was carried out using the results obtained by the fatigue experiment. The estimated fatigue life was verified through a twisting load test of the real drive shaft in a test rig.