• Journal of the Society of Disaster Information
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• v.16 no.1
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• pp.144-154
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• 2020

Purpose: This paper is a fundamental study on the applicability of the smart bolt developed for monitoring system to detect the leakage of water supply valve. Method: A leak detection experiments were conducted using the smart bolt having embedded strain sensors and accelerometer. The smart bolt used in study meets the allowable criteria of torque and tensile stress for water supply system, and it can be applied to a joint of the water supply valve by behaving well within the allowable limits. Result: As a result of the simulated leak tests, a leak signal at the valve leak point was detected in a band of 60Hz, and the main pipe leaking point was observed to produce a leak signal having much higher frequency than that of the valve leak point. This seems to result in a total coupled vibration under unconfined conditions of the pipes. Conclusion: The smart bolts appeared applicable to detecting a leaking signal from the water supply valve.

• Journal of the Korean Geosynthetics Society
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• v.19 no.4
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• pp.21-32
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• 2020

As the global large-scale infrastructure construction market expands, the construction of civil engineering structures in extreme environments such as cold or hot regions is being planned or constructed. Accordingly, the construction of the pile foundation is essential to secure the bearing capacity of the upper structure, but there is a concern about loss of stability and function of the pile foundation due to the possibility of ground deformation in extreme cold and hot regions. Therefore, in this study, a new type of pile foundation is developed to respond with the deformation of the ground, and the ground deformation that can occur in extreme cold and hot region is largely divided into heaving and settlement. The new type of pile foundation is a form in which a cylinder capable of shrinkage and expansion is inserted inside the steel pipe pile, and the effect of the cylinder during the heaving and settlement process was analyzed numerically. As a result of the numerical analysis, the ground heaving caused excessive tensile stress of the pile, and the expansion condition of the cylinder shared the tensile stress acting on the pile and reduced the axial stress acting on the pile. Ground settlement increased the compressive stress of the pile due to the occurrence of negative skin friction. The cylinder must be positioned below the neutral point and behave in shrinkage for optimum efficiency. However, the amount and location of shrinkage and expansion of cylinder must comply with the allowable displacement range of the upper structure. It is judged that the design needs to be considered.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.101-106
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• 2011

There are various methods in the flat panel display manufacture. The cost reduction effect is very big in case of using the screen printing method. The screen printing method is much used in the process of forming PDP barrier and can apply to the process of arranging the pillars for maintaining the vacuum gap of the vacuum glazing panel. The pillar which is one of the core elements for comprising vacuum glazing maintains the vacuum gap overcoming the vacuum pressure difference with the atmospheric pressure generated in vacuum glazing. At the same time, the deformation phenomenon by vacuum pressure is relived. In this paper, by using FEM about three considered in the pillar design and arrangement kinds of limiting factors, the simulation was performed. The pillar optimum arrangement method at within the maximum allowable tensile stress and heat transfer coefficients according to the arrangement try to be presented based upon the analyzed result data review and this validity tries to be verified by FEM.

• Wind and Structures
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• v.37 no.3
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• pp.245-254
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• 2023

In this paper, the wind-induced response of Jiayuguan wooden building (world cultural heritage) in Northwest China was studied. ANSYS finite element software was used to establish four kinds of building models under different working conditions and carry out modal analysis. The simulation results were compared with the field dynamic test results, obtaining the model which reflects the real vibration characteristics of the wooden tower. Time history data of fluctuating wind speed was obtained by MATLAB programming. Time domain method and ANSYS were used to analyze the wind-induced vibration response time history of Jiayuguan wooden building, obtaining the displacement time history curve of the structure. It was suggested that the wind-induced vibration coefficient of Jiayuguan wooden building is 1.76. Through analysis of the performance of the building under equivalent static wind load, the maximum displacement occurs in the three-story wall, gold column and the whole roof area, and the maximum displacement of the building is 5.39 cm. The ratio of the maximum stress value to the allowable value of wood tensile strength is 45 %. The research results can provide reference for the wind resistant design and protection of ancient buildings with similar structure to Jiayuguan wooden tower.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.237-250
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• 2015

Underground structures such as a tunnel have been considered as safer than structures on the ground during earthquake. However, severe damages of underground structures occurred at subway tunnel during 1995 Kobe Earthquake and such damages are gradually increased. In this study, a dynamic behavior of a cut and cover tunnel surrounded by weathered soils is investigated using Mohr-Coulomb Model. Parametric study was carried out for boundary conditions, tensile strength, and earthquake magnitudes. The results of numerical analyses in terms of ground deformations and stresses acting on the lining were quite dependent on the side boundary condition (free or fix conditions) and tensile strength of surrounding soils. The ground was deformed upward at the end of earthquake when the side boundary condition was fixed, whereas residual deformations were not predicted when it was free. When the tensile strength of a soil was set to the same as its cohesion, residual deformation was less than 1cm, regardless of side boundary conditions or input accelerations. In addition to that, stress conditions at the maximum deformation and end of earthquake were within an allowable range and considered as safe. Proper boundary conditions and material properties such as tensile strength are quite important because they may significantly impact on the results of dynamic analyses.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.151-161
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• 2017

A TSL (Thin Spray-on Liner) has a higher initial strength and faster construction time than conventional cementitious shotcrete. Because of its high adhesion and tensile strength, the TSL reinforced concrete show a characteristic like composite materials. In this study, to consider an application to the conventional design method, ASD (allowable stress design), numerical study was used. In the numerical analysis, material and contact properties were adopt from previous studies. Then a thickness of concrete in the tunnel was evaluated with the TSL reinforced case by the ASD concept. In other words, bending compressive stress, bending tensile stress and shearing force of the concrete were considered to determine a thickness of concrete lining by the given boundary conditions. From the numerical analysis, there was no tendency to show by the ASD because the ASD is based on the elastic theory while the TSL typically contributes to reinforcement after yielding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.721-728
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• 2017

High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.53-66
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• 2023

In this study, the results of the elasto-plastic beam analysis, finite element analysis and optimization design of the steel pipe sheet pile applied as an earth retaining wall under the deep excavation were presented. Through this study, it was found that the high-strength and sea resistant steel pipe has high allowable stress, excellent structural properties, favorable corrosion, and high utilization as an earth retaining wall, and the C-Y type joint has significantly improved the tensile strength and stiffness compared to the traditional P-P type. In addition, it was investigated that even if the leak or defect of the wall occurs during construction, it has the advantage of being able to be repaired reliably through welding and overlapping. In the case of steel pipe wall, they were evaluated as the best in views of the deep excavation due to the large allowable bending stress and deformation flexibility for the same horizontal displacement than CIP or slurry wall. Elasto-plastic and finite element analysis were conducted in consideration of ground excavation under large-scale earth pressure (uneven pressure), and the results were compared with each other. Quantitative maximum value were found to be similar between the two methods for each item, such as excavation behavior, wall displacement, or member force, and both analysis method were found to be applicable in design for steel pipe sheet pile wall. Finally, it was found that economical design was possible when determining the thinnest filling method with concrete rather than the thickest hollow shape in the same diameter, and the depth (the embedded length through normality evaluation) without rapidly change in displacement and member force.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.275-285
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• 2015

This experimental study presents the fatigue evaluation of a precast deck connected using Ultra-High Performance, Fiber Reinforced Concrete (UHPFRC). Four types of two identical large-scale specimens were fabricated with simplified splice rebar details which had a short splice length of ten times rebar diameter. The flexural behavior of each type of specimens until failure was investigated and fatigue behavior of the same type of specimens was then evaluated using two-million cyclic loading. In the flexural tests, tensile rebars exhibited the deformation exceeding yielding strain but failure mode related to the splice details was not observed in spite of such a short splice length. In the fatigue tests, damage was not appreciably accumulated by the cyclic loading except initial flexural cracks and the stress variations in tensile rebars was less than the allowable stress range. These experimental results demonstrate that all types of specimens exhibited acceptable fatigue performance and indicate that enhanced mechanical properties of ultra-high performance material permits to use a simplified splice details along with short joint width.

• KCI Concrete Journal
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• v.14 no.1
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• pp.36-42
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• 2002

Flexural behaviors of the two typical precast beam sections (inverted tee and rectangular) for buildings were investigated and compared. The height of web in the inverted tee beam was generally less than half of beam depth to be adapted to that of the nib in the ends of double-tee where the total building height limited considerably. The inverted-tee beams were designed for a parking live load - 500kgf/$m^2$ and a market - 1,200kgf/$m^2$ from the currently used typical shape of a domestic building site in Korea. The area and bottom dimension of rectangular beams were the same as those of inverted tee beams. These woo beams were also reinforced with a similar strength. following results were obtained from the studies above; 1) the rectangular beam is simpler in production, transportation, and erection, and more economic than the inverted tee beam in the construction test for these two beams with a same dimension and a similar strength, 2) all of the beams considered in the tests were generally failed in values close to those of the strength requirements in ACI Provisions. The ratios of test result to calculated value are averaged to 1.04. One rectangular and one inverted tee beams failed in a value only 2-3％ larger than the estimated volue of the Strength Design Methool the results of the Strain Compatibility Method wire slightly more accurate than those of the Strength Design Method, 4) the maximum deflections of all of the beams under the full service loads were less than those of the allowable limit in ACI Code Provisions. The rectangular beams experienced more deflection then inverted tee in the same loading condition and failed with more deflection, and 5) the rectangular and inverted tee beams showed good performances under the condition of service and ultimate loads. However, one inverted tee beams with fm span developed an initial flexural crackings under 88％ of the full service load even though they designed to satisfy the ACI tensile stress limit provisions.