• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.423-433
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• 2012

The axial load on the concrete-filled steel tube (CFT) column produces confinement stress, which enhances strength of the core concrete. The amount of strength increase in concrete depends on the magnitude of produced confinement stress. From nonlinear analyses, the ultimate resisting capacity of the CFT columns subjected to axial loads was calculated. Nonlinear material properties such as Poisson's ratio and stress-strain relation were considered in the suggested model, and the maximum confining stress was obtained by multi axial yield criteria of the steel tube. This proposed model was verified by comparing the analytical results with experimental results. Then, regression analyses were conducted to predict the maximum confining stress according to D/t ratio and material properties without rigorous structural analysis. To ensure the validity of the suggested regression formula, various empirical formulas and Eurocode4 design code were compared.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1724-1725
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• 2011

본 논문에서는 LED 패키지의 방열문제를 해결하기 위해 FR4 PCB에 Via-hole을 형성함으로써 열전달 능력을 향상시키고자 하였다. 또한 FR4 PCB의 면적과 Via-hole 크기 및 수량을 변화를 주어 그에 따른 K-factor를 측정 하였으며 열 저항 특성을 분석하였다. 결과로서, Via-hole을 형성한 FR4 PCB의 경우 초기 면적이 증가함에 따라 열 저항 및 접합온도가 급격히 감소하는 특성을 보였으며 200 [mm2]에서 안정화 되는 특성을 보였다. 또한 PCB 면적 및 Via-hole을 형성함에 따라 광 출력이 최대 17% 향상 되었다. 따라서 접합온도 및 열 저항에 있어서 PCB면적의 증가 및 Via-hole을 구성함에 있어 열전달 능력을 향상시킬 수 있음을 확인하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.69-80
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• 2008

In this study, improved capacity spectrum method (CSM) is proposed. The method can account for higher mode contribution to the seismic response of MDOF systems. The CSM has been conveniently used for determining maximum roof displacement using both demand spectrum and capacity curve of equivalent SDOF system. Unlike the conventional CSM, the maximum roof displacement is determined without iteration using inelastic displacement ratio and R factor calculated from demand spectrum and capacity curve. Three moment resisting steel frames of 3-, 9- and 20-stories are considered to test the accuracy of the proposed method. Nonlinear response history analysis (NL-RHA) for three frames is also conducted, which is considered as an exact solution. SAC LA 10/50 and 2/50 sets of ground motions are used. Moreover, this study estimates maximum story drift ratios (IDR) using ATC-40 CSM and N2-method and compared with those from the proposed method and NL-RHA. It shows that the proposed CSM estimates the maximum IDR accurately better than the previous methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.129-135
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• 2021

Rock sheds are a type of rockfall protection facility that is installed on the road near steep slopes, where large amount of rockfall is expected. Rock sheds are generally designed to resist approximately 200 kJ to 3,000 kJ of rockfall energy. In a previous study, a new type rock shed structure having a concrete-filled tube (CFT) main frame was proposed. By using CFT as the main frame in a rock shed, rapid construction is possible. Additionally, high load carrying capacity and ductility can be achieved. The behavior of the proposed rock shed structure was studied via elastic analysis with the equivalent static load of rockfall energy as in a previous study. However, it is necessary to investigate the behavior of the proposed rock shed in more detail with a full 3D finite element (FE) model considering realistic rockfall load. The FE model for the CFT rock shed main frame was developed first in this study. Then, the resistance of the CFT rock shed main frame Under ultimate rockfall energy was investigated.

• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.457-468
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• 2006

An experimental study was performed to investigate the maximum energy dissipation and the ductility capacity of shear-dominated steel plate walls with thin web plates. Three specimens of three-story plate walls with thin web plates were tested. The parameters for the test specimens were the aspect ratio of the web plate and the shear strength of the column. A concentrically braced frame and a moment-resisting frme were a also tested for comparison. The steel plate walls exhibited much better ductility and energy dissipation capacity than the concentrically braced frame and the moment-resisting frame. The results showed that unlike other structural systems, the sh as well as strength, and can therefore be used as an effective earthquake-resisting system. A method of predicting the energy dissipation capacity of a steel plate wall was proposed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.506-515
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• 2003

Six barley varieties that showed different degree of drought tolerance were grown with and without drought stress treatment (control), and investigated for the temporal changes in growth and several physiological traits after drought treatment. Soil water potential was -0.05 ㎫ at the initial stage of drought treatment and dropped to -0.29 ㎫ at 19 days after withholding irrigation. Soil water potential (SWP) maintained at -0.05 ㎫ in the control. The dry weight (DW) under the drought treatment were reduced compared to the control as follows: Dicktoo-S (short awn), 69% ; Dicktoo-L (long awn), 70%; Dicktoo-T (tetra), 86%; Dongbori-1, 69%; Suwonssalbori-365, 55% and Tapgolbori, ,37%. Dicktoo lines and Dongbori-1 were more tolerant than Suwonssalbori-365 and Tapgolbori. Leaf relative water contents (RWC) and leaf water potential (LWP) decreased obviously under the drought condition, the decrease being greater especially in the less drought-tolerant barley genotypes. Dongbori-1 and Dicktoo-L in drought treatment showed net photosynthesis of 38% and 17% compared to the control, respectively, and the other four genotypes much lower photosynthesis of 1.1% to 7.0%. Stomatal conductance, mesophyll conductance, and the photochemical efficiency (Fv/Fm) of PS II were reduced by drought treatment, the reduction being greater in drought-sensitive genotypes. The drought-tolerant genotypes had greater osmotic adjustment (OA) capacity under water stress. Thus, the decrease of RWC and LWP was lower and the turgor pressure conservation capacity was higher under water stress in drought-tolerant genotypes. Drought-tolerant genotypes showed less decrease of photosynthesis because stomatal conductance, mesophyll conductance and the ratio (Fv/Fm) of the variable to maximal fluorescence of drought-resistant genotype was decreased less in the drought stress condition. In conclusion, the drought-tolerant genotypes had better water conservation capacity through efficient OA, and this led to the lower decrease of photosynthesis and growth in water stress condition.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.630-635
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• 2022

Copper(II) oxide (CuO), electroless plated on a nitrogen-containing carbon sponge prepared by a melamine sponge thermal treatment, was developed as a nitric oxide (NO) gas sensor that operates without a wafer. The CuO content on the surface of the carbon sponge increased as the plating time increased, but the content of nitrogen known to induce NO gas adsorption decreased. The untreated carbon sponge showed a maximum resistance change (5.0%) at 18 min. On the other hand, the CuO plated sample (CuO30s-CS) showed a maximum resistance change of 18.3% in 8 min. It is considered that the improvement of the NO gas sensing capability was caused by the increase in hole carriers of the carbon sponge and improved movement of electrons due to CuO. However, the NO gas detection resistance of the CuO electroless plated carbon sponge for 60 s decreased to 1.9%. It is considered that the surface of the carbon sponge was completely plated with CuO, resulting in a decrease in the NO gas adsorption capacity and resistance change. Thus, CuO-plated carbon sponge can be used as an effective NO gas sensor because it has fast and excellent resistance change properties, but CuO should not be completely plated on the surface of the carbon sponge.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.29-36
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• 2010

To investigate the cyclic characteristics of exterior joints in RC frame buildings which are typically used after 1988, 70% scaled T-shaped beam-column subassemblies were designed and tested with a displacement control that is composed of 9 steps, until 3.5% story drift was reached. Axial forces are applied to columns during the experiment to simulate a real situation. The results show that the non-seismic detailed specimens failed before reaching 0.85% story drift, and their strengths are less than 0.85 times the nominal flexural strength which beam or columns should reach. The relationship of principal stress and story drift of exterior joints is similar to the one that Priestly proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.131-143
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• 2009

Under transverse earthquake shaking, arching action of bridge structures develops along the deck between the abutments thus providing the so-called deck resistance. The magnitude of the arching action for bridge structures is dependent on the number of spans, connection condition between deck and abutment or piers, and stiffness ratio between superstructure and substructure. In order to investigate the arching action effects for inelastic seismic responses of PSC Box bridges, seismic responses evaluated by pushover analysis, capacity spectrum analysis and nonlinear time-history analysis are compared for 18 example bridge structures with two types of span numbers (short bridge, SB and long bridge, LB), three types of pier height arrangement (regular, semi-regular and irregular) and three types of connection condition between superstructure and substructure (Type A, B, C). The arching action effects (reducing inelastic displacement and increasing resistance capacity) for short bridge (SB) is more significant than those for long bridge (LB). Semi-regular and irregular bridge structures have more significant arching action than regular bridges.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.113-121
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• 2004

A test program was conducted on full-scale steel moment connections constructed using a T-stiffener. In the T-stiffener connection, the beam-to-column connection was reinforced with the horizontal and vertical element of the T-stiffener to resist moment under severe cyclic loads. A total of five specimens were tested in this study together with a concrete-filled tubular(CFT) column(${\sqsubset}-500{\times}500{\times}12$) and a steel beam($H-506{\times}201{\times}11{\times}19$). For the specimens, the T-stiffener was combined with RBS (also known as "Dog-bone") detail or Horizontal Element Hole(HEH) detail constructed to enhance deformation capacity. The test program showed excellent seismic performance for specimens constructed with an RBS or an HEH. except the specimens had brittle failure of VE. The test results also showed that the connections all developed maximum moments at the face of the column. Such moments were at least 15% and as much as 36% larger than the plastic moment capacity of the beam. based on the actual yield stress of the beam steel.