• Composites Research
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• v.29 no.1
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• pp.1-6
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• 2016

Low-speed impact was localized on a stiffened composite structure, using 4 FBG sensors with 100 kHz-sampling rate interrogator and devised localization algorithm. The composite specimen consists of a main spar and several stringers, and the overall size of the specimen's surface is about $0.8{\times}1.2m$. Pre-stored reference data for 247 grid locations and 36 stiffener locations are gathered and used as comparison target for a random impact signal. The proposed algorithm uses the normalized cross-correlation method to compare the similarities of the two signals; the correlation results for each sensor's signal are multiplied by others, enabling mutual compensation. 20 verification points were successfully localized with a maximum error of 43.4 mm and an average error of 17.0 mm. For the same experimental setup, the performance of the proposed method is evaluated by reducing the number of sensors. It is revealed that the mutual compensation between the sensors is most effective in the case of a two sensor combination. For the sensor combination of FBG #1 and #2, the maximum localization error was 42.5 mm, with average error of 17.4 mm.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.180-189
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• 2002

The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo dynamic test has been done for four(4) test specimens which were nonseismically or seismically designed by the related provisions of the Korea roadway bridge design specification, and four nonseisemic test specimens retrofitted with fibers in the plastic hinge region. Glass and carbon fiber sheets were used for the seismic capacity enhancement of circular test specimens. Important test parameters were confinement steel ratio, load pattern, and retrofitting. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.7 ∼8.7 displacement ductility was observed for nonseismic test specimens retrofitted with fibers subjected to Korea Highway Cooperation artificial earthquake motions. It is concluded that these retrofitted test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.285-291
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• 2011

In this study the mechanical performance of the new wave dissipating block is evaluated through experiment and numerical analysis. Also, by selecting adequate reinforcement, the improvement of the structural performance is examined. The reinforcement is designed by predicting the amount of tensile force and the location where the tensile stress develops in the new wave dissipating block through numerical analysis. The new wave dissipating block is reinforced with the ordinary steel bars and the fiber reinforced plastic(FRP) bars which have advantages in ocean environment in terms of corrosion and fatigue. The test result shows that the fracture resistance of the un-reinforced concrete block is 350 kN which is about 6.2 times that of the weight of the block. All the test blocks which are reinforced by either steel of FRP bars show strength capacity of over 900 kN which is the maximum load of the test equipment. Although the single reinforcement with larger-diameter bars has advantage in terms of construction convenience, it is recommended to use multiple number of smaller-diameter bars in order to reduce the crack width.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.563-574
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• 2006

The objective of this study is to determine the effect of the loading size on displacements of stiffened plates with open ribs using the orthotropic rigidity ratio as the parameter. To analyze the displacement behavior of stiffened plates according to the loading size, a concentrated load and three types of uniform distributed loads were applied on the rib at the center of some plates. The results of the analysis of various stiffened plates show that the central displacement ratio of the distributed load to the concentrated load increased according to the decrease in the loading size, and that the ratio can be expressed as a function of the rigidity ratio for each rib space. The maximum displacement of the stiffened plate subjected to the distributed load did not appear at the center of the plate due to the local behavior, and the increasing ratio of the maximum displacement to the central displacement can be expressed as a function of the rigidity ratio for each rib space. Orthotropic plate analysis can achieve more accurate results using the proposed functions, and the application of the functions to examples of a different aspect ratio and support condition shows good accuracy. Therefore, using the functions proposed in this study, the central and maximum displacements can easily be achieved in the orthotropic plate analysis of stiffened plates subjected to the distributed load.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.159-169
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• 2007

The behavior of fiber-reinforced cemented sands (FRCS) was studied to improve a brittle failure mode observed in cemented sands. Nak-dong River sand was mixed with ordinary Portland cement and a Polyvinyl alcohol (PVA) fiber. A PVA fiber is widely used in concrete and cement reinforcement. It has a good adhesive property to cement and a specific gravity of 1.3. A PVA fiber has a diameter of 0.1 mm that is thicker than general PVA fiber for reinforced cement. Clean Nak-dong River sand, cement and fiber at optimum water content were compacted in 5 layers giving 55 blows per layer. They were cured for 7 days. Cemented sands with a cement/sand ratio of 4% were fiber-reinforced at different locations and tested for unconfined compression tests. The effect of fiber reinforcement form and distribution on strength was investigated. A specimen with evenly distributed fiber showed two times more strength than not-evenly reinforced specimen. The strength of fiber-reinforced cemented sands increases as fiber reinforcement ratio increases. A fully reinforced specimen was 1.5 times stronger than a specimen reinforced at only middle part. FRCS behavior was controlled not only by a dosage of fiber but also by fiber distribution methods or fiber types.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.178-182
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• 2008

Automotive manufacturers lay their eyes on the new manufacturing technologies because of the strengthened competition. Among them, a simultaneous forming is one of the innovative forming technologies to be able to reduce production time and cost. Several parts can be simultaneous manufactured by process, while the conventional stamping demands the same number of die sets with the number of parts. In this study, the automotive front side member was manufactured by the simultaneous forming. The position and the size of initial blank were determined by forming analysis and try-outs, and the blank movement during the forming was controlled by introducing the pilot pin.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.23-24
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• 2019

In this study, analysis of steel fiber orientation and distribution inside fiber reinforced concrete was performed using micro-CT scanning technology. Samples were extracted from the column according to its height and distance from the mold. Samples were scanned in order to attain the image of steel fibers then region of interest were obtained by binarization process. By calculating the principle moment of inertia of each fiber, direction vector, scale, center postion, volume, and surface area were gained in order to analyze the orientation and distribution. Most of the fibers inside the column tended to be perpendicular to the main axis of the column. Moreover, most of the fibers appeared at the bottom of the column and at the position where it is farthest from the mold.

• Composites Research
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• v.33 no.6
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• pp.377-382
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• 2020

The free vibration characteristics of corrugated laminated composite plates with axial stiffeners is investigated using the Rayleigh-Ritz method. The plate is stiffened by beams with open cross-section area. The equivalent homogenization model is used for the corrugated laminated composite plates. This homogenization model is treated a corrugated plate as an orthotropic plate that has different material properties in two perpendicular directions. The motion of equivalent plate is represented on the basis of the first order shear deformation theory (FSDT) to account for the effect of rotary inertia and transverse shear deformation. Stiffeners are considered as discrete elements to predict the local vibration mode to be generated by the presence of stiffeners. To validate the proposed analytical approach, natural frequencies and vibration mode shapes from the analytical method are compared with those from the FEA by ANSYS.

• Geotechnical Engineering
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• v.35 no.5
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• pp.25-38
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• 2019

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.41-49
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• 2017

In this study, we tried to confirm the influence range in the ground due to Bulbed, Reinforcement change and ground conditions change through numerical analysis. By checking the increase width of the reinforcement effect accompanying the increase of Bulbed, grasping the trend accompanying the change of the ground conditions and deciding soil nail Reinforcement and Bulbed, so that economical construction will be carried out It can be judged that it can be utilized as basic material. In this paper, we analyzed the Displacement due to positional load of reinforcement by utilizing MIDAS GTS NX which is a universal numerical analysis program. In addition, it is necessary to ensure the diameter star economy of Bulbed size and Reinforcement by comparing / analyzing whether the Bulbed relaxation region of Reinforcement represents arbitrary characteristics in the ground in Sandy soil, Weathered granite soil ground due to soil nail pullout load Numerical analysis was conducted to select criteria that can be done.