• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.2
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• pp.31-37
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• 1997

Structural details of the three-bay-straw-roof house which was the most common form of residence as a commoner's house during ancient period are suggested. Wooden frames are used in the house. The typical form of joint used is Sagaemachum. The static lateral loading capacity of the frames is evaluated through the test on full scale models. The effects of joint type at the column head and wooden lattice on the lateral loading capacity and the failure modes of frames are analyzed. The ultimate lateral loading capacity and displacement of the ordinary frame at failure are 1.090 N and 400 mm(1/6rad), respectively. These values for the frame with high column are 4,160 N and 250 mm(1/9.6rad), respectively. The behavior of joint at column head controls the overall lateral loading capacity of the frame and shows very large nonlinearity. The general failure modes of joint for an ordinary frame and a frame with high column are shear and bending failure at the branches of Sagaemachum, respectively.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.87-95
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• 2018

PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS : From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empirical-mechanical finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analy pavement-design analysis using thesis and bonding property tests using cored specimens from public roads will be conducted in further research.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.198-203
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• 1995

The objective of this study is to provide the information on the techniques of manufacturing and experiment in small scale modeling of precast concrete(P.C.)large panel structures. The adopted scale was 1/5th 4types of experiments were performed : material tests for model concrete and model reinforcement, compressive test of horizontal joint, shear test of vertical joint and cyclic static test of 2-story subassemblage structure. Based on the experimental results, the following conclusions are drawn: (1)Model concrete may have in general larger compressive strength than expected. (2) Model reinforcement can show less ductility if the annealing processes were performed without using vaccuum tube. (3) Failure modes of horizontal and vertical joints were almost same for both prototype and model. But the strength of model appears to be higher than required by similitude law. (4)Hysteretic behavior of 1/5 scale subassemblage model can be made quite similar to prototype's if the ductility of model reinforcement and compressive strength of model concrete could be representative of those of prototype.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.5
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• pp.78-83
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• 2000

When a sea-dike is constructed on soft soils, it is much difficult to calculate ground deformation caused by forced displacements. In this study , a series of laboratory model tests have been performed to investigate the ground deformation under a constructed sea-dike on soft soils. Construction sequence of sea-dike embankment was assumed such as constructed by quarry first and followed by soils adjacent to quarry embankment. as test data and displacement in subsoils have been analyzed, it seems that deformation is caused by general shear failure. the shape of ground deformation caused by forced displacements was well defined be parabola . Upon comparing profiles and depth of forced displacement from the model test to those based on stress-baring capacity method commonly used, it has been found that deformation prediction using stress-bearing capacity method was not exact at the edge of loading.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.874-882
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• 2008

In a domestic, HSR-350x which has the maximum speed 350km/h was developed and then next, the next generation high speed train which has the maximum speed 400km/h has still been developing. With developing the next generation high speed railway, there need to be a general plan to make sure of dynamic safety though the a study on the crack and failure of rail by rolling contact fatigue. Therefore, this study investigated occurring stress of rail according to the track quality, train velocity, wheel radius, track stiffness, distance between sleepers, axial force using Eisenmann's equations. For the more, via the finite element method, it investigated shear force on the rail head which could be changed by the early crack length, angle and temperature. As a result, this study confirmed the main elements which effect on the fatigue life cycle of rail.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.639-650
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• 2019

Time-domain commercial codes are widely used to evaluate the seismic behavior of tunnels. Those tools offer a good insight into the performance and the failure mechanism of tunnels under earthquake loading. Viscous damping is generally employed in the dynamic analysis to consider damping at very small strains in some cases, and the Rayleigh damping is commonly used one. Many procedures to obtain the damping parameters have been proposed but they are seldom discussed. This paper illustrates the influence of the Rayleigh damping formulation on the tunnel visco-elastic behavior under earthquake. Four Rayleigh damping determination procedures and three soil shear velocity profiles are accounted for. The results show significant differences in the free-field and in the tunnel response caused by different procedures. The difference is somewhat decreased when the soil site fundamental frequency is increased. The conventional method which consists of using solely the first soil natural mode to determine the viscous damping parameters may lead to an unsafe seismic design of the tunnel. In general, using five times site fundamental frequency to obtain the damping formulation can provide relatively conservative results.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.25-34
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• 2011

In general, many instrumentations of slope rely on theory or experience because on-site accessibility and long term instrumentation are difficult to conduct the instrumentation of slopes. Also the prediction of disaster is very difficult. Therefore experimental research was conducted about an effective method to predict collapse of slope and on-site applicability in this study. The collapse of slope was able to be predicted by applying AE sensor which we call WEAD to the failure criteria. The parameters of AE generated during the collapse of slope were secured through bending shear test. Test construction was applied to the slope with a history and a possibility of collapse. As a result, it is shown that AE parameters do not exceed the failure criterion and is found to be stable slopes. As the real symptoms of collapse did not appear, AE was found to have excellent applicability.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.151-160
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• 1999

A series of laboratory tests for the marine clay sampled under the sea of Kwangyang bay have been conducted. The main types of tests are the general index property tests, the oedometer tests and the triaxial compression tests in both undrained(CIU) and drained(CID) conditions. The clayey samples, classified as CL, CH with natural water content of 38.3~84.6% and liquidity index of 0.71~0.98, are in the normally consolidated state with O.C.R. of 1.0l~l.60. The undrained stress path from CIU tests can be normalized with isotropic consolidation pressure$(p_0)$ and equal shear strain contour is linear passing through the origin in the (q, p) plot. The undrained shear strain is found to be the only function of the stress ratio($\eta$) and linear with intercept in the ($\varepsilon/\eta,\eta$) plot. The built-up pore pressure normalized with pc is also linear with respect to $\eta$. and its slope is defined by ´C´ as a pore pressure parameter. Equations to predict the undrained stress path and the shear strain are proposed. It is proved that the proposed equations give better agreements to the measured values than the Cam-clay theories. The failure points of the stress path are located on the same C.S.L. in (q, p) plot during both CIU and CID tests, which justifies the concept of critical state theory.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.34-34
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• 2012

Heavy storms rainfall has caused many landslides and slope failures especially in the mountainous area of the world. Landslides and slope failures are common geologic hazards and posed serious threats and globally cause billions in monetary losses and thousands of casualies each year so that studies on slope stability and its failure mechanism under rainfall are being increasing attention of these days. Rainfall-induced slope failures are generally caused by the rise in ground water level, and increase in pore water pressures and seepage forces during periods of intense rainfall. The effective stress in the soil will be decreased due to the increased pore pressure, which thus reduces the soil shear strength, eventually resulting in slope failure. During the rainfall, a wetting front goes downward into the slope, resulting in a gradual increase of the water content and a decrease of the negative pore-water pressure. This negative pore-water pressure is referred to as matric suction when referenced to the pore air pressure that contributes to the stability of unsaturated soil slopes. Therefore, the importance is the study of saturated unsaturated soil behaviors in evaluation of slope stability under heavy rainfall condition. In an actual field, a series of failures may occur in a slope due to a rainfall event. So, this study attempts to develop a numerical model to investigate this failure mechanism. A two-dimensional seepage flow model coupled with a one-dimensional surface flow and erosion/deposition model is used for seepage analysis. It is necessary to identify either there is surface runoff produced or not in a soil slope during a rainfall event, while analyzing the seepage and stability of such slopes. Runoff produced by rainfall may result erosion/deposition process on the surface of the slope. The depth of runoff has vital role in the seepage process within the soil domain so that surface flow and erosion/deposition model computes the surface water head of the runoff produced by the rainfall, and erosion/deposition on the surface of the model slope. Pore water pressure and moisture content data obtained by the seepage flow model are then used to analyze the stability of the slope. Spencer method of slope stability analysis is incorporated into dynamic programming to locate the critical slip surface of a general slope.

• Advances in concrete construction
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• v.6 no.3
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• pp.245-268
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• 2018

The numerical investigations have been carried out on deep beam with opening subjected to static monotonic loading to demonstrate the accuracy and effectiveness of the finite element based numerical models. The simulations were carried out through finite element program ABAQUS/CAE and the results thus obtained were validated with the experiments available in literature. Six simply supported beams were modelled with two square openings of 200 and 250 mm sides considered as opening at centre, top and bottom of the beam. In order to define the material behaviour of concrete and reinforcing steel bar the Concrete Damaged Plasticity model and Johnson-Cook material parameters available in literature were employed. The numerical results were compared with the experiments in terms of ultimate failure load, displacement and von-Mises stresses. In addition to that, seventeen beams were simulated under static loading for studying the effect of opening location, size and shape of the opening and depth, span and shear span to depth ratio of the deep beam. In general, the numerical results accurately predicted the pattern of deformation and displacement and found in good agreement with the experiments. It was concluded that the structural response of deep beam was primarily dependent on the degree of interruption of the natural load path. An increase in opening size from 200 to 250 mm size resulted in an average shear strength reduction of 35%. The deep beams having circular openings undergo lesser deflection and thus they are preferable than square openings. An increase in depth from 500 mm to 550 mm resulted in 78% reduced deflection.