• Computers and Concrete
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• 제16권2호
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• pp.209-222
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• 2015

This paper presents results of biaxial compressive tests and strength criterion on two replacement percentages of recycled coarse aggregate (RPRCA) by mass for plain structural recycled aggregate concrete (RAC) at all kinds of stress ratios. The failure mode characteristic of specimens and the direction of the cracks were observed and described. The two principally static strengths in the corresponding stress state were measured. The influence of the stress ratios on the biaxial strengths of RAC was also analyzed. The experimental results showed that the ratios of the biaxial compressive strength ${\sigma}_{3f}$ to the corresponding uniaxial compressive strength $f_c$ for the two RAC are higher than that of the conventional concrete (CC), and dependent on the replacement percentages of recycled coarse aggregate, stress states and stress ratios; however, the differences of tensile-compressive ratios for the two RAC and CC are smaller. On this basis, a new failure criterion with the stress ratios is proposed for plain RAC under biaxial compressive stress states. It provides the experimental and theoretical foundations for strength analysis of RAC structures subject to complex loads.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제27권7호
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• pp.920-928
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• 2003

The objective of the present study was to investigate the characteristics of flow and wall shear stress under steady and pulsatile flow in the aneurysm. The numerical simulation using the software were carried out for the diameter ratios ranging from 1.5 to 3.0, Reynolds number ranging from 900 to 1800 and Womersley number, 15.47. For steady flow, it was shown that a recirculating vortex occupied the entire bulge with its core located closer to the distal end of the bulge and the strength of vortex increased with increase of the Reynolds number and diameter ratio. The position of a maximum wall shear stress was the distal end of the aneurysm regardless of the Reynolds number and diameter ratios. For the pulsatile flow, a recirculating flow at the bulge was developed and disappeared for one period and the strength of vortex increased with the diameter ratio. The maximum values of the wall shear stress increased in proportion to the diameter ratio. However, the position of a maximum wall shear stress was the distal end of the aneurysm regardless of the diameter ratios.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.361-364
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• 2004

This paper predicts the shear stress-strain relationship of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered bending moment and axial force effects. Nine columns with various shear span-to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Shear stress-strain relationship obtained from TATM was agreed well with test results conducted by bis study than other truss models.

• Journal of Korean Society of Steel Construction
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• 제16권1호통권68호
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• pp.103-111
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• 2004

This paper dealt with the local buckling of H-beams investigated mainly using the parameters of load ratios. load conditions, and support boundary condition considering predicted uniformly elevated temperatures. The physical properties of the material at elevated temperatures followed EC3 Park 1.2. The local buckling of the plates in steel beams show that they are governed by the yield stress or the critical stress of the steel plates according to the ratios of b/tf, d/tw. The evaluation of uniformly heated steel beams on the local buckling considered the stress and moment ratios to the LRFD.

• Journal of Korean Society of Steel Construction
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• 제17권4호통권77호
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• pp.491-498
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• 2005

This study involves the development of a computer program to analyze the local buckling stresses for the flange and the web of I-beams under compression at elevated temperatures, and the optimization algorithm to analyze the optimum width-thickness ratios which does not occur their local buckling prior to yield failure. The high-temperature stress-strain relationships of steel used in this study were based on EC3 (Eurocode3) Part1.2 (2000b). In this study, the local buckling stresses and the optimum width-thichness ratios were analyzed considering the influences of the yield stress, local buckling coefficients and width-thickness ratios of the flange and the web. Design examples show the applicability of the computer program developed in this study.

• The Korean Journal of Health Service Management
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• 제13권3호
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• pp.149-162
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• 2019

Objectives: The purpose of this study was to identify differences in characteristics of the people who frequently drink alone between those in old-city regions and those in other regions in Busan, focusing on socio-demographic factors and the level of drinking according to the types of stress. Methods: The analysis confirmed the differences based on Busan Social Statistics Data in 2012, 2014, and 2016. Frequencies by each variable were presented, and ${\chi}^2$ and logistic regression analysis were also used in the analysis. Results: The residents of Busan showed higher odds ratios of "frequent drinking alone" when they felt considerably higher-than-normal levels of stress. In addition, in the residents of old-city regions, the odds ratios of those who frequently drank alone were not different between people who could easily relieve stress, who experienced economic stress, or who had relationship stress and people who did not. However, higher odds ratios of frequently drinking alone were reported when such participants felt some stress related to work, family, relationships, and so on. Conclusions: Interventions for the appropriate relief of stress caused by different reasons, as well as other stress-relieving methods, should be implemented for the people's benefits.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1989-1995
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• 2004

Finite element analysis(FEA) is the most popular numerical method to simulate plasticity-induced fatigue crack closure and can predict fatigue crack closure behavior. Finite element analysis under plane stress state using 4-node isoparametric elements is performed to investigate the detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The mesh of constant size elements on the crack surface can not correctly predict the opening level for fatigue crack as shown in the previous works. The crack opening behavior for the size mesh with a linear change shows almost flat stress level after a crack tip has passed by the monotonic plastic zone. The prediction of crack opening level presents a good agreement with published experimental data regardless of stress ratios, which are using the mesh of the elements that are in proportion to the reversed plastic zone size considering the opening stress intensity factors. Numerical interpolation results of finite element analysis can precisely predict the crack opening level. This method shows a good agreement with the experimental data regardless of the stress ratios and kinds of materials.

• Journal of the Korea institute for structural maintenance and inspection
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• 제16권4호
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• pp.9-17
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• 2012

In the previous research, allowable compressive stress was analyzed based on strength theory, in which primary effect factors on the allowable compressive stress, such as eccentricity ratio, section type, section size, prestress and self-weight moment, were considered. As its results, allowable compressive stress equations were proposed. As a series of the previous research, this paper presents an experimental study on the prestress at transfer of pre-tensioned members with different eccentricity ratios. The results shows that ACI318-08 and EC2-02 are unconservative for the members under low eccentricity ratios, and they are conservative for the members under high eccentricity ratios. Compared to the code provisions, the results indicates that the proposed equation reasonably well evaluates the allowable compressive stresses for those with different eccentricity ratios.

• Textile Coloration and Finishing
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• 제12권2호
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• pp.103-110
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• 2000

To examine the physical properties of POY through the microstructure control, the crystal structure such as the crystallinity, the crystallite size, the orientation, the shrinkage, the tensile properties, and the thermal stress of POY(80/48, SD) were examined at different draw ratios and annealing temperatures. From the examination following conclusions were obtained : 1. The crystallinity was more effected by the heat setting temperature than by the draw ratio. The increasing rate was greatest at the heat setting temperature range of $170~190^\circ{C}$. 2. The crystallite size perpendicular to the fiber axis was more effected by the annealing temperature at lower draw ratios. On the other hand, the crystal and amorphous orientations were more effected by the heat setting at higher draw ratios. 3. The boiling shrinkage did not change significantly, but the total shrinkage showed 13% at the draw ratio 1.9 and the heat setting temperature $170^\circ{C}$. 4. The maximum thermal stress increased with increasing the draw ratio and decreasing the heat setting temperature in the temperature range of $170~210^\circ{C}$. At the draw ratio 1.9 and the heat setting temperature $170^\circ{C}$, the maximum thermal stress found was 1.1gf/d. 5. In the heat setting temperature above $170^\circ{C}$ after the drawing, the crystallinity, the crystallite size, the orientation, and the strength increased with increasing temperature, but the shrinkage and the maximum thermal stress decreased with increasing temperature.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.13-18
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• 2004

The objective of this study is to investigate fracture toughness and fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (RAFs) JLF-I. The fracture toughness tests were performed with various size(plane size and thickness) and various side groove of specimens. The fatigue crack propagation behavior of the JLF-I steel was investigated by the constant-amplitude loading test for the stress ratios R=O.I, 0.3 and 0.5 respectively. The effects of stress ratios and specimen size on the fatigue crack growth behaviors for JLF-I steel were discussed within the Paris law. The test results showed the standard CT specimen with the side groove of 40 % represented a valid fracture toughness. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. However, the fracture resistance curve of half size specimen was similar to that of the standard specimen. The fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. The fatigue crack propagation behavior of this material were evaluated by using a half size specimen.