• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.199-208
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• 2011

The purpose of this study is to evaluate of the strength and deformation capacity of metallic dampers with the variable slit shape. For this purpose, 12 metallic damper specimens were prepared and shear testing was performed. According to the test results, the S shaped metallic damper with the strut height of 200mm and angle of $60^{\circ}$ shows better hysteretic performance than any other specimens. By making a comparison between the yield strength in test and the proposed strength formula, test results shows larger yield strength than calculation method.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.71-81
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• 2005

Surface wave techniques were initially based on 2-D plane waves and were later improved to the techniques based the 3-D based cylindrical waves. However, body-wave interference, near-field effect and limited technology in surface wave measurements restricted the use of 3-D cylindrical waves to the 1-D evaluation of subgrade stiffness. In this study, by the numerical simulation of SASW measurements, the dispersion properties of surface waves including vertical, horizontal Rayleigh waves and Love waves were thoroughly investigated in the 3-D domain, and a new filter criteria to minimize the near-field effect was established, which led to CAP (common-array-profiling)-SASW technique. The CAP-SASW technique enabled the evaluation of subgrade stiffness fur a specific subgrade segment, not for a whole section of measurement array. Therefore, a contour plot of subgrade stiffness with a ground-truth quality can be obtained by the CAP-SASW technique. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.

• 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 Korean Society of Hazard Mitigation
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• v.2 no.2 s.5
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• pp.105-113
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• 2002

Steel-Concrete composite girders have been used since early in the 1920's due to their advantages, which are lower weight, increasement of stiffness, slenderness, long span. However, in designing short to continuous composite bridges, negative moment occurs in mid-support and creates problems such as cracks in the concrete slab. Therefore, partially composite bridges are considered. In this time, slab-anchor is used in these. If the stiffness of shear connectors is insufficient, slip would happen at the contact surface. Partial interaction is the case that takes account of slips. In this paper, the evaluation of initial shear stiffness of slab-anchor in composite bridges is obtained from Push-Out specimen. Also, finite element analyses which uses the initial shear stiffness of slab-anchor got the experiment are carried out on simple composite girder and continuous composite girder. Futhermore, the ratio of composite according to various shear stiffness are investigated and the classification according to the ratio of composite is proposed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.137-146
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• 2007

Numerical analyses are performed to show the effect of stiffening facade riggers on the behavior of the structure and to investigate the optimum locations of facade riggers. Optimum locations of the facade riggers to minimize the drift at the top of the structure are obtained by maximizing the drift reduction caused by the facade riggers and are significantly influenced by the bending and shear stiffnesses of the braced frame and facade riggers. Three standard load cases of uniformal and triangularly distributed lateral loads as well as a lateral point load at the top of the structure are considered in this paper Optimum locations of facade riggers are plotted as functions of nondimensional relative stiffness parameters ${\omega}$ and ${\beta}$ for structures with one to four riggers. Although the analysis presented herein is based on certain simplifying assumptions, it is believed that the results do provide sufficiently accurate information for determining the optimum locations of facade riggers in highrise structures.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.26-36
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• 2008

As the height of the light-framed building increases, the lateral load and overturn-moment are increased and the possibility of the building overturn becomes larger. Because the shear wall resists lateral load in light-framed building, the reinforcement of shear wall is required. In order to reinforce the light-framed shear wall, using lag screw fastener type (B-HD) and using bolt type (S-HD) hold-down connectors were applied for test. And domestic larch lumbers, $38{\times}140mm$ and $89{\times}140mm$, KS 2nd grade, were used for the stud. The North American OSB panels were used for sheathing panel. Static loads, load speed 6 mm/min, were applied on top of the wall. As a result, shear strength of the wall that using hold-down connector was improved sufficiently. And when applying the S-HD type hold-down connector, stud should be reinforced against weakening by drilled hole. As increasing the number of lag screw, the number of bolt and the product allowable strength, the strength of shear wall that using hold-down connector was also increased. When applying hold-down connector to light-framed building using 38 mm stud, it must be reinforced by enlarging the thickness of stud like as 38 mm doubled column.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.53-62
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• 2008

A constitutive model, which can simulate the effect of principal stress rotation associated with direct simple shear test, is proposed in this study. The model is based on two mobilized planes. The plastic strains occur from the two mobilized planes, and depend on stress state, and they are added. The first plane is a plane of maximum shear stress, which rotates about the horizontal axis, and the second plane is a horizontal plane which is spatially fixed. The second plane is used to consider the effect of principal stress rotation on simple shear tests under different stress states. The soil skeleton behavior observed in drained simple shear tests is captured in the model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC. The model is first calibrated with drained simple shear tests on loose Fraser River sand. The measured shear stress and volume change are partially induced by principal stress rotation and compared with model calculations. The model is verified by comparing predicted and measured settlements due to rigid footing resting on loose sands. Settlements predicted by the proposed model were very similar to measured settlements. Mohr-Coulomb model can not consider the effect of principal stress rotation and its prediction was only 20% of measured settlements.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.60-67
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• 1995

The factors affecting on the fatigue strength of spot_welded specimens have been studied. The influence of initial overloads on the fatigue life of spot_welded tensile_shear specimens is investigated by considering fatigue crack initiation and crack propagation. The change of strain range and the influence of initial overload are correlated on the basis ol strain results. The results of this study are as follows. l) The initial absolute strain range decreased with initial overloads increase, and absolute strain range decreased before transformation of waveform of strain, but increased after transformation of waveform of strain. 2) In case of subsequent point of inflection of offset strain, the increment of this strain decreased with initial overload increase. 3) As initial overloads increase, the deformation behavior of spot welded parts is restricted after overloading.

• Composites Research
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• v.30 no.2
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• pp.132-137
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• 2017

The purpose of this paper is to investigate failure characteristics of Carbon/BMI-Nomex honeycomb sandwich on design parameters. A total of 6 types sandwich specimens were manufactured according to core height, face thickness and density, and environmental condition were applied to evaluate temperature and humidity effects of one of these specimens. The test results show that the core shear buckling loads was commonly observed in all specimens except for the joint with density of $64kg/m^3$. After core shear buckling, however, the joint carried additional loads over the buckling loads and then finally failed in the upper face and lower face at the same time. In the case of specimen having high stiffness, the maximum failure load was low due to interfacial failure of the upper face and core without initial core shear buckling. The ETW1 and ETW2 conditions, which were carried out to evaluate the environmental condition of the sandwich specimen, show an initial failure mode which was significantly different from RTD condition. Also, the ETW2 condition with increased temperature under the same humidity shows that the core shear buckling load was 18% less than ETW1 condition.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.93-101
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• 2008

Bearing strength test was investigated to determine the bearing properties of domestic larix glulam according to the load direction (in parallel to grain and in perpendicular to grain), the fastener (bolt and drift-pin), and the direction of laminae. The specimen was 5 ply glulam. The diameters of fastener are 12, 16 and 20 mm. The results were as follows. 1) In according to the diameter of bolt and drift-pin, the average of maximum bearing strength in parallel to grain loading was similar to that in perpendicular to grain loading. The average of maximum bearing strength was 1.50~2.31 times higher in parallel to grain loading than in perpendicular to grain loading. The average of maximum bearing strength in parallel to grain loading was lowered by 20% with increasing the diameter from 16 mm to 20 mm, but that in perpendicular to grain loading didn't show a clear tendency. 2) The average of bearing stiffness in parallel to grain loading was the highest at 16 mm in diameter. The average of bearing stiffness is similar to the shearing stiffness in drift-pin connection with increasing diameter. 3) In parallel to grain loading, the failure mode of specimens was the splitting along the grain in decreasing diameter. The failure mode in perpendicular to grain loading was the splitting along the grain. In this case, split occured more in specimens using bolt than in those using drift-pin. 4) The 5% offset yield strength in parallel to grain loading was similar to the predicted bearing strength of KBCS, NDS. In perpendicular to grain loading, the NDS's equation can be applied to predict the bearing strength.