• Structural Engineering and Mechanics
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• v.71 no.6
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• pp.699-712
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• 2019

The reinforced concrete lining of hydraulic pressure tunnels tends to crack under high inner water pressure (IWP), which results in the inner water exosmosis along cracks and involves typical hydro-mechanical interaction. This study aims at the development, validation and application of an indirect-coupled method to simulate the lining cracking process. Based on the concrete damage plasticity (CDP) model, the utility routine GETVRM and the user subroutine USDFLD in the finite element code ABAQUS is employed to calculate and adjust the secondary hydraulic conductivity according to the material damage and the plastic volume strain. The friction-contact method (FCM) is introduced to track the lining-rock interface behavior. Compared with the traditional node-shared method (NSM) model, the FCM model is more feasible to simulate the lining cracking process. The number of cracks and the reinforcement stress can be significantly reduced, which matches well with the observed results in engineering practices. Moreover, the damage evolution of reinforced concrete lining can be effectively slowed down. This numerical method provides an insight into the cracking process of reinforced concrete lining in hydraulic pressure tunnels.

• Smart Structures and Systems
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• v.20 no.3
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• pp.343-350
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• 2017

An experimental study is presented of the application of fiber Bragg grating (FBG) interrogation method based on optical time-domain reflectometery (OTDR) to monitoring strain in bent reinforced concrete beams. The results obtained with the OTDR-based method are shown to agree well with the direct spectral measurements. Strain sensitivity, resolution and measurement range amounted to $0.0028dB/{\mu}strain$; $30{\mu}strain$; $4000{\mu}strain$, correspondingly. Significant differences are observed in surface and inner deformations of the test beams which can be attributed to different mechanical properties of concrete and steel reinforcement. The prospects of using OTDR-based FBG interrogation technique in real-life applications are discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1035-1038
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• 2007

We designed and manufactured a 1.8T high temperature superconducting(HTS) insert coil for a NMR magnet operated at 4.2 K. Suitable HTS superconductor and HTS coil were carefully designed and developed. We have selected multi-filamentary Bi2223 conductor fabricated by American Superconductor Corporation(AMSC). The selected conductor consists of Bi2223 filaments of 55, silver stabilizer and stainless steel reinforcement tapes. Therefore, it shows good hoop strength as well as compression tolerance. The conductor has a tape cross-section of 0.31mm x 4.8mm. the Bi2223 conductor shows large anisotropy of critical current. The critical current of conductor in magnetic field parallel to the flat surface are much higher than that in magnetic field perpendicular. The HTS coil has an inner diameter of 78 mm, an outer diameter of 127 mm and a coil length of 600 mm. In this paper, the detailed design, fabrication and test results on the HTS insert coil are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.725-730
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• 1998

In the nuclear power plant, steel or polymer liner plates are adopted to prohibit inner concrete surface contacting with gas or liquid materials. If there is an accident, the plate will be damaged, and concrete shall have final responsibility to safety requirements. In this paper, an experimental research was carried out to investigate the effects of construction joint and wet and loading condition on the permeability of concrete. The test results showed that leakage rate is decreased much more at the following cases than the others : (a)wet condition, (b)without a construction joint case, and (c)case subjected to external loads. It was noted that more reinforcement is required at the latter case.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.5
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• pp.676-682
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• 2009

The idler wheel installed at the front side of the newly developed tracked vehicle didn't meet the durability requirement by showing the crack failure near the jointed region at the wheel during the field test. To find the crack developing mechanism we constructed finite element model for the idler wheel representing the behavior of interface between each suspension units, material properties from the material test data and actual loading conditions. This paper shows a result that maximum von Mises stress near the bolt hole on the outer rim is higher than inner idler coressponding to the actual test result and that result was reversed by adopting the reinforcement outside of the outer rim.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.99-104
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• 2002

Recently, the continuous fiber materials has become more important materials to repair and to reinforce concrete structural members. Continuous fiber meshes are effective for shear and confining reinforcement and provide excellent durability when combined with high strength mortar The purpose of this study is to verify the relationship between concrete strength and the ductility of inner concrete confined laterally by continuous fiber meshes. For this study, Experimental studies were conducted by compressive members using the cast frame of high strength mortar and continuous fiber meshes. Therefore, the result shows that compressive strength and ductility has improved according to the amount of the fiber meshes, and that the lateral confined effect of members with 3- or 4-axis mesh arrangement is bigger than that of members with 2-axis mesh. These data have to be used to verify the characteristic of concrete structure members reinforced continuous fiber mesh.

• Structural Engineering and Mechanics
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• v.78 no.3
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• pp.297-303
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• 2021

In this paper, a mathematical model is used to the evaluation of thermoelastic interactions in fiber-reinforced material with a spherical cavity. With the goal of establishing the generalized thermoelastic model with thermal relaxation time are exploited. inner surface of the spherical cavity is tractions free and loaded by the uniform step in temperature. The finite element scheme is used to get the problem numerical solutions. The numerical results have been discussed graphically to show the impacts of the presence and the absence of reinforcement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.195-202
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• 2006

Thin-walled structures are efficiently utilized an automobiles, aircraft, satellite and ship as well as needed light weight simultaneously. This paper presents new shape of automobile hood reinforcement that rotating parts as engine, transmission are protected by thin-walled structures. The automobile hood is concerned about the resonance occurs due to the frequency of the rotating parts. The hood must be designed by supporting the stiffness of design loads and considering the natural frequencies. Hence, it is sustained the stiffness and considered the vibration by resonance. It is deep related to ride. Therefore, the topology, shape and size optimization methods are used to design the automobile hood. Topology technique is applied to determine the layout of a structural component optimum size with maximized natural frequency by volume reduction. In this research, The optimal structure layout of an inner reinforcement of an automobile hood for the natural frequency of a designated mode is obtained by using topology optimization method. The optimum size and the optimum shape are determined by PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.230-236
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• 2020

A trash screen is installed in front of the inflow channel of a drainage pumping station, sewage treatment plant, and a power plant to block floating contaminants. The bottleneck phenomenon, which decreases the water inflow, causes damage to the damper as a result of clogging in between the screen if string type obstacles are not removed. In this paper, the apron was removed, and the screen was expanded, to prevent breakage of the bottleneck phenomenon and string type obstacles. This was designed using an extended rake by adding an inner rake in between the screen interspace to remove the bottleneck phenomenon and string type obstacles. To design the inner rake that satisfies the allowable stresses of the existing damper rake, the experiment points were determined according to the experimental design method using the inner rake vertical length and the thickness of the reinforced section as parameters. The use of the ANSYS static structural module and statistical analysis tool R software gives the optimized shape according to the response surface method. The relative error between the response surface analysis results and the simulation results was 1.63% of the determined optimal design-point rake length of 210.2 mm and the reinforcement section thickness of 2 mm. Through empirical experiments, a test rake was constructed to the actual size, and approximately 97% of the bottleneck phenomenon and string type obstacles could be removed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.404-411
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• 2009

The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the load-movement relations and the reinforcement effect by the outer steel pipe in the steel-concrete composite pile were analyzed by performing three-dimensional numerical analyses, which can simulate the yielding behavior of the pile material and the elasto-plastic behavior of soils. The parameters analyzed in the study include three pile materials of steel, concrete and composite, pile diameter and loading direction. As the results, the axial capacity of the composite pile was 1.9 times larger than that of the steel pipe pile and similar with that of the concrete pile. At the allowable movement criteria, the horizontal capacity of the composite pile was 1.46 times larger than that of the steel pile and 1.25 times larger than that of the concrete pile. In addition, the horizontal movement at the pile head of the composite pile was about 78% of that of the steel pile and about 53% of that of the concrete pile, which showed that the movement reduction effect of the composite pile was significant and enables the economical design of drilled shafts.