• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.316-322
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• 2009

This paper presents a preliminary study to monitor the lateral behavior of pile foundation using multiplexed fiber Bragg grating(FBG) sensors. In the Preliminary study, an 1.7 meter long cantilever beam with the shape of square hollow box was fabricated and tested under the static loading. Four FBG sensors were multiplexed in a single optical fiber and installed into the top and bottom of the cantilever beam. The strains are directly measured from FBG sensors followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the regression analyses based on the geometric relationships. It has been found that excellent correlation with conventional sensing system was observed. The success of the test encourages the use of the FBG sensing system as a monitoring system for pile foundations. However, further consideration should be given in the case of the sensor malfunction for the practical purpose.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.271-287
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• 2013

In this study, more convenient model(S-model) for predicting ground surface settlement is developed through comparing field monitoring data of the domestic subway applied shield TBM method with conventional equation & numerical analysis. Sample stations are chosen from whole of excavation section and lateral & vertical ground surface settlement characteristic with excavation are analysed. Based on analysis result, through the comparison with actual monitoring data, the model that is possible to compute maximum surface settlement and settlement influence area is suggested with assumption that lateral surface settlement forms are composed relaxed zone and elastic zone. In addition, vertical ground surface settlement patterns with excavation are similar to cubic-function and S-model with assumption that coefficients are function of tunnel diameter and depth is suggested. Consequently, the ground surface settlement patterns are significantly similar to actual monitoring data and numerical method result. Thus, as a result, when tunnels are excavated using sheild TBM through rather soft weathered soil & rock layer, prediction of ground surface settlement with excavation using convenient S-model is practicable.

• The korean journal of orthodontics
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• v.29 no.4 s.75
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• pp.411-424
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• 1999

The purpose of this study was to find the difference of stress distribution of initial compressive and tensile stress when anterior section of upper utility arch was activated crown lingual torque of $5^{\circ},\;10^{\circ},\;15^{\circ}$ through three-dimensional finite element analysis. For this study the finite element model of upper central and lateral incisors, 1st. and 2nd. premolars and 1st. molars and each periodontal membrane and upper utility arch were made. From the solutions of ANSYS the followings were obtained. 1. $5^{\circ},\;10^{\circ},\;15^{\circ}$ crown lingual torque produce the almost similar distribution and measurement of initial compressive and tensile stress. 2. Acivated upper utility arch torqued central inciors lingually and lateral incisors labially.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.23-31
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• 2007

Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.

• Journal of Bio-Environment Control
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• v.10 no.1
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• pp.36-41
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• 2001

This experiment was carried out to investigate temperature distribution in the double layer plastic greenhouse and chilling injury to watermelons grown during a cold season. Temperatures on eastern and western sides were about 6.2% and 14.7%, respectively, lower than that of central section in a south-north oriented greenhouse. Daily mean temperature in the northern part was about 1-2$^{\circ}C$ higher than that in the southern part of the greenhouse. In terms of vertical temperature distribution inside the greenhouse, temperature at ground surface was approximately 1$^{\circ}C$ lower during the day and 0.5$^{\circ}C$ higher during the night than that in the upper part, 2m from the ground surface. Leaf mould medium kept higher ground temperatures as compared to sandy soil, red clay soil, and in the northern and southern sides as compared to the central part of the greenhouse. A symptom of chilling injury on leaves was upward curling, followed by chlorosis and necrosis. A severe symptom of chilling injury to plants was the breakdown of vascular bundles. Root growth was more susceptible than stem or leaf growth to low temperatures. At 3$0^{\circ}C$, main and lateral roots grew vigorously, while lateral root growth was inhibited at 22$^{\circ}C$ and root growth was stopped at 14$^{\circ}C$ and 6$^{\circ}C$. Small and puffy fruits with dark green surface were produced at low temperatures. In cold season cultivation of watermelons, it is suggested that plants be transplanted in the central part and train to sides of the greenhouse in order to reduced chilling injuries.

• The Korean Journal of Soil Zoology
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• v.5 no.2
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• pp.101-112
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• 2000

Spiders usually have poor vision but not the jumping spiders. Their eight eyes are located on its distinctive box-shaped head and relatively well developed. The Spiders were fixated with 3% glutaraldehyde and thin section was performed with ultra-microtome. The specimens were observed with light microscopy, transmission and scanning electron microscopy. Eye area of jumping spider is competed of three rows. The first eye row comprise four eyes. Among them, two anterior median eyes are the largest and two anterior lateral eyes are relatively small. The former are main-eyes and have excellent vision. The second row, which has the two smallest eyes, is located about midway between the first and third rows. The third row is about half-way back on the thorax and eyed of which are middle size. To investigate ultrastructure of salticid spiders'eye, Menemerus fulvus was chosen. All of Menemerus fuvus's eyes are composed of cornea, lens, vitreous body and retina in histologically. Cornea layer, linked to exocuticle of exoskeleton. is regular layer structure without any cell tripe. Lenses are biconvex type. Retinas comprise well developed microvilli-shape rhabdomeres, unpigmented supporting cells, and pigmented cell. Retinas of anterior median eyes are surrounded by circular cylinder-shaped vitreous body, photoreceptor, i.e. rhabdomeres, of it is irregularly arranged compared to the other eyes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.503-515
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• 2017

Underground structures that have recently become larger are required to be stable not only during normal times but also during earthquakes. Especially, it is very important to maintain the stability of the subsea tunnels during the earthquake. The objective of this paper is to verify the effectiveness of the flexible segment, which is one of the breakthrough facilities to maintain the stability of the subsea tunnel during the earthquake using the shaking table test. Another goal of this paper is to propose the optimum position of the flexible segment through 3D dynamic numerical analysis based on the verified results from shaking table tests. The 1g shaking table test considering the similarity ratio (1:100) to the cross section of the selected artificial subsea tunnel was carried out considering the Geongju and Artificial seismic waves, longitudinal and lateral wave, and with/without flexible segments eight times or more. As a result of the shaking table test, it was confirmed that the flexible segment is effective in improving the seismic performance of the undersea tunnel in all the experimental results. In addition, 3D dynamic numerical analysis was performed to select the optimum position of the flexible segment which is effective for improving seismic performance. As a result, it was confirmed that the seismic acceleration is attenuated when the flexible segment is installed adjacent to the branch section in subsea tunnel.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.405-414
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• 2006

In the present study, a numerical analysis was performed for interior connections of continuous flat plate to analyze the effect of design parameters such as column section shape, gravity load and slab span on the behavioral characteristics of the connections. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases and gravity load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. And as the slab span loaded with relatively large gravity load increases, the negative moment around the connection increases and therefore the strength of connection against unbalanced moment decreases. By considering the effect of design parameters on the strength of the connections, the effective shear strength to calculate the torsional moment capacity of connection was proposed and the effectiveness of the proposed shear strength was verified.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.45-56
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• 1999

Seismic refracrion and reflection surveys were conducted along an E-W trending track of 482 m long in Ilwall-dong, Pohang. End-on spread was employed as source-receiver configuration with 2 m for both geophone interval and offset. Seismic data were acquired using 24 channels at every shot fired every 2 m along the track. Refraction data were interpreted using equations for multi-horizontal layers. Reflection data were processed in the sequence of trace edit, gain control, CMP sorting, NMO correction, mute, common offset gathering, and filtering to produce a single fold seismic section. There are two layers in shallow subsurface of the study area. Upper layer has the P-wave velocities ranging from 267 to 566 m/s and is interpreted as a layer of unconsolidated sediments. Lower layer has P-wave velocities of 1096-3108 m/s and is interpreted as weathered rock to hard rock. Most of the lower layer classified as soft rock. Upper layer has lateral variations in both P-wave velocity and thickness. The upper layer in the eastern part of the seismic line is 3-5 m thick and has P-wave velocity of 400 m/s in average. The upper layer in the western part is 8-10 m thick and has P-wave velocity of 340 m/s in average. The eastern part is interpreted as unconsolidated beach sand, while the western part is interpreted as infilled soil to develop a construction site. Three fault systems of high angle are imaged in seismic reflection section. It is interpreted that the area between these fault systems are relatively safe. Large buildings should be located in the safe ground condition of no fault and footings should be designed to be in the basement rock of 3-10 m deep below the surface.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.71-80
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• 2004

The failure of cut slopes frequently occurs particularly during the thawing season and the rain season in summer. This study interpreted data collected from site to which a real-monitoring system was applied in order to analyze the causes of ground behaviors and to forecast future slope failure. As for research methods, this study analyzed the size and mechanism of failure by integrating the results of field surveys and measurements. Furthermore, it analyzed data transmitted by the monitoring system installed in the a result, three times of ground displacement occurred as well as a number of partial tension cracks. The cut slope composed of sandstone and siltstone started its initial behavior as a result of torrential downpour and the loss of support of the substructure. For quantitative analysis of the characteristics of ground behavior, this study measured 5 lateral lines. According to the result of the measurement, displacement happened little in the section to which countermeasure had been applied, but displacement of maximum 400mm happened in the section to which countermeasure had not bee applied. The analysis of data on displacement and rainfall suggested a close relationship between ground behavior and rainfall. According to the result of stability interpretation along with the change of ground saturation, stability rate appeared to be less than 1.0 when ground saturation is over 55%. Although the current trend of ground behavior is at a stable stage falling within the range of tolerance, it is considered necessary to continue monitoring and data analysis because ground displacement is highly possible with the change of temperature during the winter.