• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1177-1192
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• 2018

The objective of this study is to develop the existing drainage system for catching the partial leakage of tunnel structures operating in cold region. The drainage system consists of drainage board, Hotty-gel as a waterproofing material, cover for preventing protrusion of Hotty-gel, air nailer, fixed nail, pipe for collecting ground leak, pipe for conveying ground leak, wire-mesh, and sprayed cement mortar. The drainage systems were installed in conventional concrete lining tunnels to evaluate the site applicability and constructability. The performances of waterproof and the drainage in the drainage system were evaluated by injecting 1,000 ml of red water in the back of the drainage system at 7 days, 14 days, 21 days, 28 days, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months and 8 months. During 8 months of field test, the average daily temperature of the tunnel site was measured from $-16.0^{\circ}C$ to $25.6^{\circ}C$. The daily minimum temperature was $-21.3^{\circ}C$ and the daily maximum temperature was $30.8^{\circ}C$. There was no problem in waterproof and drainage performance of the drainage board in the drainage system. However, the pipe for conveying ground leak had the leakage problem from 14 days. It is considered that the leakage of the pipe for conveying ground leak was caused by the deformation of the pipe of the flexible plastic material having a thickness of 0.2 cm by using the high pressure air nailer and the fixing pin and the insufficient thickness and width of the hotty-gel for preventing the leakage.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.311-318
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• 2018

When reinforced concrete structures are exposed to fire, their mechanical properties such as compressive strength, elasticity coefficient and rebar yield strength, are degraded. Therefore, the structure's damage assessment is essential in determining whether to dismantle or augment the structure after a fire. In this study, the confinement effect of lateral reinforcement of RC column according to the numbers of fire exposure face and stirrup was verified by fire resistant test with the heating temperatures of $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$. The test results showed that the peak stress decreases and peak strain increases as the temperature is getting higher, also transverse ties are helpful in improving the compressive resistance of concrete subjected to high temperature. Based on the results of this study, the residual stress of confined concrete under thermal damage is higher at the condition of more lateral reinforcement ratio and less fire exposure faces. The decreasing ratio of elastic modulus of more confined and less exposure faces from the relationship of load and displacement was also smaller than that of opposite conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.1-8
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• 2019

Steel elevator pit was developed for the purpose of minimizing the excavation, simplifying the construction of the frame and economical efficiency by improving the problems that occurred in the existing reinforced concrete. It is common to apply conventional RC method through excavation to underground structures such as underground floor collector well and elevator pit. In recent years, the use of steel collector well and steel elevator pits to reduce construction costs by minimizing the materials of steel and concrete has been continuously increasing. The steel elevator pit is an underground structure and then the performance of the welding part and the structure system is important. Specimen with only steel plate and concrete without studs could support the load more than 3 times than the specimen with deck only. Therefore, even if there is no stud, the deck (steel plate) rib is formed and the effect of restraining the steel plate and the concrete during the bending action can be expected. However, since sudden fracture in the elevator pit may occur, stud bolt arrangement is necessary for the composite effect of steel plate and concrete. It is expected that the bending strength can be expected to increase by about 15% or more depending with and without stud bolts.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.10-19
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• 2019

Management plan with repairing is essential for RC structures exposed to chloride attack since durability problems occur with extended service life. Conventionally deterministic method is adopted for evaluation of service life and repair cost, however more reasonable repair cost can be obtained through continuous repair cost from probabilistic maintenance technique. Unlike the previous researches considering only normal distribution of life time, PLTFs (Probabilistic Life Time Function) which can be capable of handling log and normal distributions are attempted for initial and repair service life, and repair cost is evaluated for OPC and GGBFS concrete. PLTF with log distributions in initial service life is more effective to save repair cost since it is more dominant after average than normal distribution. Repair cost in GGBFS concrete decreases to 30% of OPC concrete due to longer initial service life and lower repairing event. The proposed PLTF from the work can handle not only normal distributions but also log distributions for initial and repair service life, so that it can provide more reasonable repair cost evaluation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.51-59
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• 2019

There is increasingly more research focusing on the application of FRP reinforcing bars as an alternative material for steel reinforcing bars, but most such research look at short term behavior of FRP reinforced structures. In this study, the microscopic analysis and tensile behavior of Basalt and Glass FRP bars under freezing-thawing and alkaline conditions were experimentally evaluated. After 100 cycles of the freezing and thawing, the tensile strength and elastic modulus of FRP bars decreased by about 5%. In the case of microstructure of FRP bars during the initial 20 days, no significant damages of FRP bar sections were found under $20^{\circ}C$ alkaline solution; however, the specimens immersed in $60^{\circ}C$ alkaline solution were found to experience resin dissolution, fiber damage and the separation of the resin-fiber interface. In the alkaline environment, the strength decrease of about 10% occurred in the environment at $20^{\circ}C$ for 100 days, but the tensile strength of FRPs exposed for 500 days decreased by 50%. At temperature of $40^{\circ}C$ and $60^{\circ}C$, an abrupt decrease in the strength was observed at 50 and 100 days. Especially, the tensile strength decrease of Basalt fiber Reinforced Polymer bars showed more severe degradation due to the damage caused by dissolution of resin matrix and fiber swelling in alkaline solution. Therefore, in order to improve the long-term performance of the surface braided FRPr reinforcing bars, surface treatment is required to ensure alkali resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.94-101
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• 2019

Most of the existing rail structures have undergone a lot of aging since a considerable period of time has passed from completion. In particular, among existing railway bridges, many of the plate girder bridges are older bridges that have lived 40 to 60 years or more. Since the treadmill is directly connected to the girder without the ballast, the running load of the vehicle is directly transmitted to the bridge. Therefore, the shock and noise applied to the bridge are larger than those of the ballast bridge, and the dynamic shock and vibration are also relatively large. Therefore, it is very urgent to develop appropriate maintenance, repair and reinforcement technology for existing steel plate bridge. In this study, the authors introduced the characteristics of embedded rail (ERS) developed for improving the performance of the existing plate girder bridge and the techniques solving the vibration and noise problems. In order to evaluate the vibration and noise reduction performance of ERS, a non-ballast plate girder bridge with 5m length of sleepers installed and a plate girder bridge with ERS were fabricated. And, then, the vibration response generated under the same excitation condition was measured and analyzed. Also, the radiated noise analysis was performed using the vibration response data obtained from the experiment as the input data of the acoustic analysis model. As a result of experiments and analyses, it was confirmed that the plate girder bridge's vibration using ERS was reduced by 15.0~18.8dB and the average noise was reduced by 7.7dB(A) more than the non-ballast bridge.

• Korean Journal of Heritage: History & Science
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• v.48 no.4
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• pp.74-93
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• 2015

Geophysical survey of Korea was introduced in Nara National Research Institute of Cultural Heritage in 1995. At that time, it has been activated geophysical survey of architecture and civil engineering in Korea. But there was no exploration experts to be combined the archaeology. For this reason, National Research Institute of Cultural Heritage has introduced the physical exploration. Through the expert exchanges South Korea and Japan carried out joint exploration. And it has increased the reliability of the exploration method and exploration results. It is GPR the most method commonly in geophysical exploration. There are many usability before excavation because of good resolution. However, the shallow GPR penetration depth has limitations in large mounds. We were able to take advantage of the resistivity analysis program to study the underground structure to deep through the experts exchange. We was able to get a good result that overcomes the limitations of GPR exploration in a number of burial mounds including Naju bokamri by the resistivity analysis program. In particular, we confirmed the location of the burial main body by compares the results of exploration and excavation results. In the future we will perform a convergence research of exploration and archaeology through a variety of joint research. In addition we will have to build a new network of archaeological science.

• Journal of the Korean earth science society
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• v.40 no.3
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• pp.272-282
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• 2019

Although the knowledge of current seismicity is a critical information for making and implementing effective earthquake-related policy, the detailed seismicity information of the metropolitan areas with high-population density has been largely underestimated due to the high-level of cultural noise and small earthquake magnitude. This study presents 12 earthquakes including 2 earthquakes previously known and 10 additional earthquakes occurred from 2010 to 2017 in Busan, but they were unreported by the Korea Meteorological Administration. Matched filter technique is used to detect micro-earthquakes. Although the epicenters of micro-earthquakes though present a distinguished linearity, a correlation with faults in the area is unknown. A repeated micro-seismicity suggests that there are subsurface structures responsible for observed events. If large earthquakes occur along the fault in Busan, they may cause catastrophic natural disasters. Given the fact that the recent earthquakes did not accompany any surface signatures, it is highly recommended that the current micro-seismicity be investigated, and updated seismicity information be incorporated into establishing active fault maps in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.612-620
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• 2019

The increasing use of curved beams in buildings, vehicles, ships, and aircraft has results in considerable effort being directed toward developing an accurate method for analyzing the dynamic behavior of such structures. The stability behavior of elastic curved beams has been the subject of a large number of investigations. Solutions of the relevant differential equations have traditionally been obtained by the standard finite difference. These techniques require a great deal of computer time as the number of discrete nodes becomes relatively large under conditions of complex geometry and loading. One of the efficient procedures for the solution of partial differential equations is the method of differential quadrature. The differential quadrature method(DQM) has been applied to a large number of cases to overcome the difficulties of the complex algorithms of programming for the computer, as well as excessive use of storage due to conditions of complex geometry and loading. In this study, the in-plane extensional vibration for asymmetric curved beams with linearly varying cross-section is analyzed using the DQM. Fundamental frequency parameters are calculated for the member with various parameter ratios, boundary conditions, and opening angles. The results are compared with the result by other methods for cases in which they are available. According to the analysis of the solutions, the DQM, used only a limited number of grid points, gives results which agree very well with the exact ones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.580-589
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• 2019

Indonesia has a very short supply of electricity. As a solution to this problem, plans for construction of thermal power plants are increasing. Thermal power plant require the cooling water system to cool the overheated engine and equipment that accompany power generation, and the circulation water pump chamber among the cooling water system are generally designed according to the ANSI (1998) standard. In this study, the design criterion $20^{\circ}$ for the spreading angle of the ANSI (1998) of the layout of the circulating water pump chamber can not be satisfied on the K-coal thermal power plant site condition in Indonesia. Therefore, 3-D numerical model experiment was carried out to obtain a hydraulically stable flow and stable structure. The Flow-3D model was used as numerical model. In order to examine the applicability of the Flow-3D model, the flow study results around the rectangular structure of Rodi (1997) and the numerical analysis results were compared around the rectangular structures. The longitudinal velocity distribution derived from numerical analysis show good agreement. In order to satisfy the design velocity in the circulating water pump chamber, a rectangular baffle favoring velocity reduction was applied. When the approach velocity into the circulating water pump chamber was occurred 1.5 m/s ~ 2.5 m/s, the angle of the separation flow on the baffle was occurred about $15^{\circ}{\sim}20^{\circ}$. By placing the baffle below the separation flow angle downstream, the design velocity of less than 0.5 m/s was satisfied at inlet bay.