• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.435-440
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• 2010

A numerical model, which can compute deformation of rubble mound structures composed with various size materials, was proposed. In the numerical model, wave field into the mound structures was computed by CADMAS-SURF and the deformations of mound structures were computed by DEM. Interaction between wave field and sectional deformation of structure was considered and to present the variation of behaviors caused by various properties of materials, computation was carried out with random coefficients by Monte Carlo simulation method for contact stiffness and friction angle. The experiments were carried out with rubbles and glass balls with radius of 2.9cm, 2.6cm and 1.5cm. And the deformation characteristics of rubble mounds composed with various size materials were clarified. Furthermore the validity and the applicability of the model were discussed by comparing with the experimental results.

• Geotechnical Engineering
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• v.4 no.1
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• pp.49-58
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• 1988

The stresses on the buried steel pipe under embankment are analysed by the elasto-plastic theory using FEM to study the influences of the geometry of soil-conduit pipe system and the elastic modulus of the fill on the pipe responses . The geometry of the system considered in this study includes the height of embankment, the thickness of the pipe, and the width and the depth of the trench . By comparing the stresses computed by Marston-Spangler's pipe theory with those obtained from the elasto-plastic theory, Marston-Spangler's theory was discussed and analysed . It is found that the stress distribution around the pipe by elasto- plastic analysis is similar to that by Spangler's flexible pipe theory when the geometrical ratio (diameter/thickness) of the steel pipe is 400. And Spangler's flexible pipe theory does not seem to be suitable to analyse the buried steel pipe of which the geometrical ratio is lower than 200. The vertical loads by the rigid pipe theory are always larger than those by the flexible pipe theory regardness of the variations in the geometry of soil-conduit pipe system considered above and the elastic modulus of the fill.

• Journal of the Korean GEO-environmental Society
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• v.13 no.7
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• pp.5-12
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• 2012

Recently the installation of reinforced earth retaining walls in the domestic construction site has increased, surpassing conventional RC walls. These reinforced walls have various types depending on the reinforcing material, installation method and the form of face panel. However, there are difficulties in design and construction management due to the unproved safety of construction method. In case of reinforcing materials, despite the fact that they come in all different sizes and types produced by small businesses or partially imported with cheap price and low quality, no proper standards for designing the walls have been suggested. In order to apply reinforced retaining wall system to broad cases and design the walls effectively considering site conditions, specific design and construction guidelines for efficient construction management are needed. In conclusion, this study verified that reduction factors can be greatly affected by grain sizes and stiffness of backfill materials and granularity range, therefore in case of relatively large construction site, it is required to redesign the reinforced retaining wall by evaluating site installation resistance test, applying respective reduction factors to each backfill material and select the right geogrid depending on the usage of retaining wall so as to enhance the safety of reinforced earth retaining walls with efficiency.

• Journal of Navigation and Port Research
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• v.36 no.5
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• pp.339-347
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• 2012

After towing rope connecting a barge to a tug was subdivided into multiple finite elements, then those dynamic models was established using Newton's second law and considering the external force and moment such as tension, drag, Coriolis force, gravity, buoyancy, and impact due to free surface acting on each element. While the previous research on the model of towing rope considered only translation, five-degree-of-freedom equations of motion except roll based on the body-fixed frame were established in this paper. All elements are connected by a spring and a damper, and the stiffness of the spring was set as the equivalent value of the real rope. In order to confirm the established multiple finite element model, various scenarios such as freely falling of towing rope in the air and above the free surface, accelerating of a tug which tows a barge connected by towing rope, and sinusoidal moving of a tug were set up and simulated. As the results, the trajectories of the tug, the barge, and the towing rope showed good tendencies to the ones of real expected situations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.109-120
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• 2007

Auxiliary support systems such as the reinforced protective umbrella method have been applied before tunnel excavation to increase ground stiffness and to prevent the large deformation. However, determination procedure of geotechnical parameters along the construction sequence contains various errors. This study suggests a method to characterize the time-dependent behavior of pre-reinforced zones around the tunnel using elastic waves. Experimental results show that shear strength as well as elastic wave velocities increase with the curing time. Shear strength and strength parameters can be uniquely correlated to elastic wave velocities. Obtained results from the laboratory tests are applied to numerical simulation of tunnel considering its construction sequences. Based on numerical analysis, initial installation part of pre-reinforcement and portal of tunnel are critical for tunnel stability. Result of the time-dependent condition is similar to the results of for $1{\sim}2$ days of the constant time conditions. Finally, suggested simple analysis method combining experimental and numerical procedure which considering time-dependent behavior of pre-reinforced zone on tunnel would provide reliable and reasonable design and analysis for tunnel.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.51-56
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• 1997

The objective of this study is to review the current state of earthquake simulation tecniques using the shaking table and check the reliability. One degree-of-freedom(d.o.f) and three d.o.f aluminium shear models were used and $4m{\times}4m$ 6 d.o.f shaking table was excitated in one horizontal direction to simulate 1940 El centro earthquake accelerogram (NS component). When the actual acceleration history of shaking table is compared to the desired one, it can be found that the overall histories are very similar, but that the lower frequency range (0~2 Hz) of the actual excitation has generally lower amplitude than that of the desired in Fourier transform amplitude. Free vibration and white noise tests have shown almost the some values for natural frequencies, but shown quite different values for damping rations, that is, 1.37% in case of free vibration test vs 14.76 % in case of white noise test. The time histories of story shear driff show the globally linear elastic behaviors. But the elliptical shape of the histories with one of the axis being the stiffness of the story implies the effect of viscous damping.

• Journal of the Korean Geotechnical Society
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• v.31 no.12
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• pp.5-15
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• 2015

The GCP (Granular Compaction Pile) for the improvement objective of soft ground has been frequently studied. However, these studies were the results deduced on the basis of the numerical analysis and the laboratory model tests, and there was no study method to apply the effects of the bulging failure of a flexible pile. In this study, the sensitivity of the load-settlement curves of the uniform and the tapered GCP dependant on the geotechnical parameters estimated from N value of standard penetration test (SPT) was analyzed. It was estimated reasonably that, in the very soft clay soil (N=3 or less), elastic modulus was 700~2000 kPa and Poisson's ratio was 0.40~0.48.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.184-192
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• 2010

The member deflection is one of the most important considerations for the serviceability evaluation of reinforced concrete (RC) structures, and the concept of the effective moment of inertia has been generally used for its estimation. However, the actual service load applied on an existing RC beam may not be easily obtained, for which the estimation of beam deflection by existing methods can be difficult to obtain. Therefore, based on the correlation between cracks and deflection in a RC beam, this study proposed a method to estimate the deflection of RC beams directly from the condition of cracks not using the actual loads acting on the member as its input data. The proposed method extensively utilized the relationships among sums of crack widths, average strains, and curvatures, and modification factors obtained from regression analysis were also introduced to improve its accuracy. The deflections of members were successfully estimated by the proposed method independent from applied loads, which was also easy to apply compared to the existing methods based on the effective moment of inertia.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.130-138
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• 1994

Bottom plates of empty hold are subjected to not only water pressure but also bi-axial inplane loads, specially in the alternate full loading full loading condition of bulk carrier. This kind of plate behaviours is very difficult to be explained and to be estimated using common buckling design guide in the initial design stage of hull structure, therefore, some more concrete studies for this plate structure was performed based on the currently developed buckling estimation formula. In this buckling formula, torsional stiffness effects of edge stiffener are included additionally and effects of elastic buckling strength of plate panel are treated as characteristic value problem. Also considering boundary stiffener effects and inplane and lateral loading, evaluation of bottom plate scantling using this formula, calculated results using various classification regulation of buckling strength and results of first report approach are compared each other and useful guides using developed formula for bottom plate scantling design are discussed.

• The Journal of Engineering Geology
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• v.8 no.2
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• pp.131-143
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• 1998

The study area, Beulgok-myon Nonsan-goon Chungcheongnan-do is consist of Changri slate(Och, okcheon system), lithic tuff(Kslt, kyoungsang system), granite (Kqb, kyoungsang system) and quartz porphyry(Kgf, kyoungsang system). More than 3000 joints were measured and classified by direction. Main dipdirection/dips of Kqb are 228~257/73~88, 010~150/70~85, Och are 134~164/40~90, 214~249/55~89, Kslt are 291~332/75~82, 235~241/73~71. But Kgf are not appeared distinct directions of joint. In field, p-wave velocities(Vp) are measured on the bed rock. Vp of Kgf are $5000m(240^{\circ})~2380(360^{\circ})m/s$, Kqb are $3846(210^{\circ})~1408(150^{\circ})m/s$, Kslt are $5000(360^{\circ})~2323(150^{\circ})m/s$ and Och are $6657(180^{\circ})~2000(030^{\circ})m/s$. Also P-wave velocities on specimen are measured. It is slightely higher than it's measured on the bed rock. For engineering properties of rock, we measured Poisson's ratio, rigidity, Young's modulus and bulk modulus by dynamic method.