• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
• /
• pp.187-190
• /
• 1994

During the initial design phases for prestressed concrete structures, the mecessary information concerning the physical properties of the hardened concrete such as creep, drying shrinkage, modulus of elasticity, and Poisson's ratio are obtained from design assumptions or accepted standards. But these assumptions may not totally reflect the actual long-term behavior of the concrete. So they may be of limited use in predicting the actual behavior. The purpose of this paper is to describe the test procedures and methods of evaluation which were used during the long-term study.

• Structural Engineering and Mechanics
• /
• 제26권4호
• /
• pp.393-408
• /
• 2007

The effects of material nonhomogeneity and nonisothermal conditions on the stress response of pressurized tubes are assessed by virtue of a computational model. The modulus of elasticity, the Poisson's ratio, the yield strength, and the coefficient of thermal expansion, are assumed to vary nonlinearly in the tube. A logarithmic temperature distribution within the tube is proposed. Under these conditions, it is shown that the stress states and the magnitudes of response variables are affected significantly by both the material nonhomogeneity and the existence of the radial temperature gradient.

• 한국통신학회:학술대회논문집
• /
• 한국통신학회 1986년도 춘계학술발표회 논문집
• /
• pp.206-210
• /
• 1986

Double Ion Implantation methods are used to improve the stiffness os carrier profiles, and then the analytical solutions to Poisson`s equation are derived with summation of each carrier profile. Numerical analyses are done using profer boudary conditions and the results show that the improvement of voltage-dependent-capacitance ratio (C(!)/C(25)) is obtained up to B.6. The third ion implantation is for the enhancement of the Schottky barrier height.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 봄 학술발표회 논문집
• /
• pp.79-86
• /
• 2002

Rock mass classifications form the back bone of the empirical design approach and are widely employed in rock engineering. In this paper the inter-relations were discussed among RMR, Q-system, RCR, N, M-RMR, RMi, and L-RMR. Several relationships for the assessment of the modulus of deformation of rock mass, Poisson's ratio, uniaxial compressive strength, tensile strength, cohesion and internal friction angle were also analysed and suggested.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
• /
• pp.140-145
• /
• 1991

Tests were conducted to get a mix proportioning of high strength concrete between σ28 and (C/W) using low quality materials easily purchased in situ. Superplasticizer was used as a chemical admixture to compensate low slump of base concrete keeping it up about 15±2㎝. General material properties such as modulus of elasticity, poisson's ratio, unit weight and stress-strain characteristic of high strength concrete were obtained. Test results show that mix proportioning of high strength concrete proposed in this paper have reasonable validity and these can be used as a design criteria in high strength concrete construction.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2006년도 학술발표회 논문집
• /
• pp.440-444
• /
• 2006

In this paper an analytical study is carried out to improve the capacity of absorbing boundary using dashpot, one of the most widely used absorbing boundaries in FEM. Using harmonic plane wave equation, absorbing boundary condition is modified to maximize its capacity according to the incident angle. Validity of the modified absorbing boundary conditions is investigated by adopting the solution of Miller-Pursey which is the solution for the wave propagation in semi-infinite elastic media, and the absorption ratio is calculated according to various Poisson's ratios.

• Structural Engineering and Mechanics
• /
• 제76권6호
• /
• pp.765-779
• /
• 2020

This article presents a nonclassical size dependent model based on the modified couple stress theory to study and analyze the bending behavior of perforated microbeams under different loading patterns. Modified equivalent material and geometrical parameters for perforated beam are presented. The modified couple stress theory with one material length scale parameter is adopted to incorporate the microstructure effect into the governing equations of perforated beam structure. The governing equilibrium equations of the perforated Timoshenko as well as the perforated Euler Bernoulli are developed based on the potential energy minimization principle. The Poisson's effect is included in the governing equilibrium equations. Regular square perforation configuration is considered. Based on Fourier series expansion, closed forms for the bending deflection and the rotational displacements are obtained for simply supported perforated microbeams. The proposed methodology is validated and compared with the available results in the literature and an excellent agreement is detected. Numerical results demonstrated the applicability of the proposed methodology to investigate the bending behavior of regularly squared perforated beams incorporating microstructure effect under different excitation patterns. The obtained results are significantly important for the design and production of perforated microbeam structures.

• Advances in concrete construction
• /
• 제10권4호
• /
• pp.345-355
• /
• 2020

In this paper, vibration characteristics of double-walled carbon nanotubes (CNTs) is studied based upon nonlocal elastic shell theory. The significance of small scale is being perceived by developing nonlocal Love shell model. The wave propagation approach has been utilized to frame the governing equations as eigen value system. The influence of nonlocal parameter subjected to diverse end supports has been overtly analyzed. An appropriate selection of material properties and nonlocal parameter has been considered. The influence of changing mechanical parameter Poisson's ratio has been investigated in detail. The dominance of boundary conditions via nonlocal parameter is shown graphically. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.

• 터널과지하공간
• /
• 제17권2호
• /
• pp.83-89
• /
• 2007

충격반향기법은 특정 매질에 충격을 가하여 매질의 동적 불성을 측정할 수 있는 비파괴 시험법이다. 본 연구에서는 암석시편에 충격반향기법을 수행할 수 있는 시험장비를 설치하고, 동적 물성치를 측정할 수 있는 시스템을 구축하였다. 이를 통해 국내 5개 지역에서 채취한 암석 시료 및 시멘트 모르타르와 알루미늄 합금에 대해 시험을 수행하여 동적 물성치를 측정하고, 1회의 충격시험으로 종파 및 횡파의 공진주파수와 감쇠비를 결정하였다. 그 결과. 동탄성계수와 정탄성계수는 10%내외의 차이를 가진 결과치가 도출되었고, 동포아송비는 정포아송비에 비해 0.07 이상 높은 값이 측정되었다. 또한 풍화도가 높거나 절리가 발달한 암석일수록 감쇠비가 증가하는 현상을 관찰하였다.

• Structural Engineering and Mechanics
• /
• 제34권2호
• /
• pp.143-157
• /
• 2010

This paper presents theoretical solutions for the three-dimensional (3D) stress field in an infinite isotropic elastic plate containing a through-the-thickness circular hole subjected to far-field in-plane loads by using Kane and Mindlin's assumption. The dangerous position, where the premature fracture or failure of the plate will take place, the expressions of the tangential stress at the surface of the hole and the out-of-plane stress constraint factor are found in a concise, explicit form. Based on the present theoretical solutions, a comprehensive analysis is performed on the deviated degree of the in-plane stresses from the related plane stress solutions, stress concentration and out-of-plane constraint, and the emphasis has been placed on the effects of the plate thickness, Poisson's ratio and the far-field in-plane loads on the stress field. The analytical solution shows that the effects of the plate thickness and Poisson's ratio on the deviation of the 3D in-plane stress components is obvious and could not be ignored, although their effects on distributions of the in-plane stress components are slight, and that the effect of the far-field in-plane loads is just on the contrary of that of the above two. When only the shear stress is loaded at far field, the stress concentration factor reach its peak value about 8.9% higher than that of the plane stress solutions, and the out-of-plane stress constraint factor can reach 1 at the surface of the hole and is the biggest among all cases considered.