• International Journal of Safety
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• v.2 no.1
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• pp.1-6
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• 2003

In this paper, several different fracture criteria using the Eftis and Subramanian's stress solutions [1] are compared with the printed experimental results under different loading conditions. The analytical results of using the solution with non-singular term show better than without non-singular in comparison with the experimental data. And maximum tangential stress criterion (MTS) and maximum tangential strain energy density criterion (MTSE) can get useful results for several loading conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.281-284
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• 2006

ASCE-ACI Committee 426 and 445, on Shear and Torsion, well noted in their report that recent research work regarding shear and torsion had been devoted primarily to members. But it was not logical approach of PSC members applied by axial force based on the shear deformation in web element. And it was not included that the effect of axial is to shift the shear strain(or crack width) in the web element versus the applied shear curve up or down by the amount by which the biaxial tension-compression state varies. The shear strength also increases or decreases, so that the change in shear strain at service load due to the presence of axial load is to some extent changed. Generally, in corresponding beams the shear strain at service load is less in the beam subject to axial compression and greater in the beam subject to axial tension, than in the beam without axial load. In particular, however, no research were available on the shear deformation in shear of PSC members with web reinforcement, subject to axial force in addition to shear and bending. Therefore, this study was basically performed to develop the program for the calculation of the shear deformation based on the shear effect of axial force in prestressed concrete members.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.479-486
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• 2011

In this study, we conducted experiment and finite element analysis on the flexural behavior of the round concrete panels according to the evaluation method of biaxial flexural tensile strengths. The Round Panel Test (RPT) and the Biaxial Flexure Test (BFT) were used to determine the biaxial flexural strength of round plain concrete panels. In order to understand the stress distribution on the panels, we measured load-strain relationship at the center of the panels' bottom surface. Test results show that fracture pattern in RPT and BFT panels are similar, and the tensile stress distribution is uniform in all directions at the center of the bottom surface of the panels for both RPT and BFT. The distribution of stresses in two test specimens coincided with the analysis result. The average biaxial flexural strength of RPT is about 29% greater than those of the BFT. The coefficient of variations (COV) of the RPT and BFT for the biaxial flexure strength is 8%, 6%, respectively, which indicates that BFT method is useful and reliable for determining biaxial flexural strengths of the concrete.

• Korean Journal of Materials Research
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• v.33 no.5
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• pp.189-194
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• 2023

This study uses first-principles calculations to investigate the mechanical properties and effect of strain on the electronic properties of the 2D material 1H-PbX₂ (X: S, Se). Firstly, the stability of the 1H Pb-dichalcogenide structures was evaluated using Born's criteria. The obtained results show that the 1H-PbS₂ material possesses the greatest ideal strength of 3.48 N/m, with 3.68 N/m for 1H-PbSe₂ in biaxial strain. In addition, 1H-PbS₂ and 1H-PbSe₂ are direct semiconductors at equilibrium with band gaps of 2.30 eV and 1.90 eV, respectively. The band gap was investigated and remained almost unchanged under the strain ε_xx but altered significantly at strains ε_yy and ε_bia. At the fracture strain in the biaxial direction (19 %), the band gap of 1H-PbS₂ decreases about 60 %, and that of 1H-PbSe₂ decreases about 50 %. 1H-PbS₂ and 1H-PbSe₂ can convert from direct to indirect semiconductor under the strain ε_yy. Our findings reveal that the two structures have significant potential for application in nanoelectronic devices.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.454-456
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• 2014

ferroelectric perovskite의 ferroelectricity를 유지하기 위해서는 oxygen vacancy를 조절해야 한다. BTO의 경우 Ti-O(vacancy site)-Ti의 align 방향에 따라 두 종류의 vacancy가 존재하는데, Ti-O-Ti가 c-axis와 평행한 경우 BTO의 ferroelectricity가 약해진다. 본 연구에서는 BTO에 ab-biaxial strain을 가해 보고, 그 결과 두 종류의 vacancy formation energy가 어떻게 변화하는지 확인하였다. 그 결과 a, b-axis의 격자 상수가 증가하면 $V_b$가 $V_c$에 비해 안정해진다는 사실을 확인하였다. 이는 BTO의 oxygen vacancy의 vacancy site에 vacancy로 인해 남는 전자가 국지화되어 Ti-vacancy site 간 인력과 Ti-Ti간 반발력이 균형을 이룰 때 vacancy의 에너지가 낮아지기 때문이다.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.69-77
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• 2003

One directional and biaxial tension tests of 13 reinforced concrete panels were conducted to derive a constitutive law of concrete. Based on the test results, a model equation is derived for the stress-strain relationship of concrete in tension. Main test variables are reinforcement ratio and the load ratio applied in two directions. In addition a failure envelope of concrete in tension-tension region is suggested based on the initial crack occurrence. Test results show that the concrete carries substantial tensile stress even after cracking occurrence. However, the application of this proposed stress-strain relationship for concrete is limited to the case where the direction of reinforcement coincides with the direction of the applied principal stresses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.452-455
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• 2008

In the present study, blow forming characteristics of commercially roiled AZ31 alloy sheets were investigated. Two different kinds of AZ31 sheets were originally fabricated by using direct casting and strip casting methods respectively. Both sheets have similar grain sizes of about $7{\mu}m$ with a relatively equiaxed structure after rolling. A series of tensile tests were carried out to get flow behavior in terms of temperature and strain rate. Also, grain size effect was investigated by annealing as-received sheet at elevated temperatures. Elongation increased with temperature increment as well expected. However, the differences in tensile test condition did not give much difference in elongation even at the temperature range where a large elongation would be expected with such as fine grain of $7{\mu}m$. Blow forming experiments showed that forming condition did not result in higher difference in dome height. However, the interesting feature from this study was that formability of this AZ31 alloy got different with stress condition. Firstly, biaxial stress condition might result in lower temperature and strain rate dependencies compared to uniaxial tension results for both DC and SC sheets. Secondly, DC showed slower grain growth in uniaxial tension than in biaxial stress state while SC has much higher grain growth rage in uniaxial tension than in bulging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06a
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• pp.156-163
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• 1998

During an actual forming operation, a material may undergo considrably large changes in strain path, and these changes can significantly alter the forming limits. So, in this study, modified forming limit curves(FLCs) in complex strain path are determined with specially designed jig to give test specimens with desired prestrains in uniaxial or biaxial deformation mode. In another part of present study, theoretical prediction of FLCs is attempted with MK's theory and Hosford's yield criterion to give forming limit curves in positive minor strain region and with Hill's local necking theory in negative minor strain region. Comparison of these theoretical results with experimental ones will be mentioned for both linear and complex strain path.

• Steel and Composite Structures
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• v.37 no.4
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• pp.405-418
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• 2020

The application of double-skin composite wall should meet different layout plans. However, most available research focused on the rectangular section with uniform axial compression. In this research, the structural behavior of double-skin composite wall with L section was studied. Due to the unsymmetric geometric characteristics, the considered loading condition combined the axial compression and biaxial bending. Five specimens were designed and tested under eccentric compression. The variables in the test included the width of the web wall, the truss spacing, the thickness of the steel faceplate, and the thickness of the web wall. The test results were discussed in terms of the load-displacement responses, buckling behavior, stiffness, ductility, strength utilization, strain distribution. Two modern codes were employed to predict the interaction between the axial compression and the biaxial bending. The method to calculate the available bending moment along the two directions was proposed. It was found that CECS 159:2004 offers more suitable results than AISC 360.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.189-200
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• 2017

Nonplanar structural walls with C-shaped and H-shaped sections have been used as an efficient lateral force-resisting system for building structures. Since the nonplanar walls are subjected to axial load and bending moments about two orthogonal axes, complicated section analysis is required for flexure-compression design. In the present study, a straightforward design method for biaxially loaded C- and H-shaped walls was proposed by modifying the existing load contour method for columns with symmetric solid sections. For this, a strain compatibility section analysis program that can calculate biaxial moment strengths of arbitrary wall section was developed and its validity was verified by comparing with existing test results. Then, through parametric study, the interaction of biaxial moments at constant axial loads in prototype C- and H-shaped walls was investigated. The results showed that, due to unsymmetrical geometry of the wall sections, the biaxial interaction was significantly affected by the moment directions and axial loads. From those investigations, non-dimensional contour equations of the biaxial moments at constant axial loads for C- and H-shaped walls were suggested. Further, design examples using the proposed contour equations were given for engineering practice.