• Title/Summary/Keyword: discontinuity function

Search Result 148, Processing Time 0.03 seconds

Fracture Analysis of Concrete using Plastic-Damage Model (소성-손상 모델을 이용한 콘크리트의 파괴해석)

  • 남진원;송하원;김광수
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • 2004.10a
    • /
    • pp.534-541
    • /
    • 2004
  • The modeling of crack initiation and propagation is very important for the failure analysis of concrete. The cracking process in concrete is quite different from that of other materials, such as metal and glass, in that it is not a sudden onset of new free surface but a continuous forming and connecting of microcracks. The failure process of concrete by cracking causes irreversible deformations and stiffness degradation. Those phenomenon can be modeled using plasticity and damage theory in macroscopic aspect. In this study, a plastic-damage model based on homogenized crack model considering velocity discontinuity and damage variable which is a function of plastic strain is proposed for fracture analysis of concrete. Finally, the plastic-damage model is verified with experimental data.

  • PDF

Load Transfer Characteristics of Rock-Socketed Drilled Shafts Considering Hole Roughness (굴착면 거칠기를 고려한 암반 근입 현장타설말뚝의 주면하중전이 특성)

  • Seol, Hoon-Il;Jeong, Sang-Seom;Woo, Sang-Yoon
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2006.03a
    • /
    • pp.494-505
    • /
    • 2006
  • In this study, using constant normal stiffness(CNS) direct shear tests, side shear load distribution were analyzed by the influencing parameters of unconfined compressive strength, surface roughness, confining stress, and material properties. Based on the CNS tests, side shear load transfer function of drilled shafts in rock is proposed using geological strength index(GSI), which indicates discontinuity and surface condition of rock mass in Hoek-Brown criterion. Though comparisons with results of nine drilled shafts's load tests, it is found that the load-transfer curve by this study is in good agreement with the general trend observed by in situ measurements, and thus represents a significant improvement in the prediction of bearing capacity of drilled shaft.

  • PDF

Management of Discon tinuous Reconstruction In the Evolution Stage of Kinetic Scheme

  • Ohwada Taku;Kobayashi Seijiro
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2003.10a
    • /
    • pp.189-190
    • /
    • 2003
  • A New kinetic scheme for the compressible Navier-Stokes equations is developed. While the conventional approach, such as KFVS scheme, employs the splitting algorithm and computes the numerical flux on the basis of the collisionless equation, the present approach employs the splitting algorithm in the evaluation of the numerical flux, where the collision effect is explicitly taken into account. However, the initial condition employed in the computation is slightly different from the conventional Chapman-Enskog NS distribution function. The present study also reveals the background of the existing kinetic schemes. such as the KFVS scheme and Gas-Kinetic BGK scheme.

  • PDF

A Study on the Stress Concentration Coefficient due to the Change of Ellipse on a Square Plate (사각 평판에서 타원의 형상 변화에 따른 응력집중계수에 관한 연구)

  • 박정호;김형준;박기훈;조우석;제승봉;김현수
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2003.06a
    • /
    • pp.1434-1437
    • /
    • 2003
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio a/b increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces. As the plate with three holes. the stress $\sigma$$\_$x/ and $\tau$$\_$xy/ of hole 1,3 becomes high, especially $\sigma$$\_$x/ dominant and high.

  • PDF

A Study on the Stress Concentration Coefficient due to the Change of Position and Shape of Ellipse on a Square Plate (사각 평판에서 타원의 위치와 형상 변화에 따른 응력집중계수의 변화에 관한 연구)

  • 최경호;권영석;박기훈;김현수
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2002.10a
    • /
    • pp.833-836
    • /
    • 2002
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio ah increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces.

  • PDF

Adaptive finite element wind analysis with mesh refinement and recovery (요소 세분화 및 재결합을 이용한 바람의 적응적 유한요소 해석)

  • 최창근;유원진;이은진
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • 1998.04a
    • /
    • pp.60-67
    • /
    • 1998
  • This paper deals with the development of a variable-node element and its application to the adaptive h-version mesh refinement-recovery for the incompressible viscous flow analysis. The element which has variable mid-side nodes can be used in generating the transition zone between the refined and unrefined elements and efficiently used for construction of a refined mesh without generating distorted elements. A modified Gaussian quadrature is needed to evaluate the element matrices due to the discontinuity of derivatives of the shape functions used for the element. The penalty function method which can reduce the number of independent variables is adopted for the purpose of computational efficiency and the selective reduced integration is carried out for the convection and pressure terms to preserve the stability of solution. For the economical analysis of transient problems, not only the mesh refinement but also the mesh recovery is needed. The numerical examples show that the optimal mesh for the finite element analysis of a wind around the structures can be obtained automatically by the proposed scheme.

  • PDF

Internal Wave Computations based on a Discontinuity in Dynamic Pressure (동압 계수의 불연속성을 이용한 내면파의 수치해석)

  • 신상묵;김동훈
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.41 no.4
    • /
    • pp.17-29
    • /
    • 2004
  • Internal waves are computed using a ghost fluid method on an unstructured grid. Discontinuities in density and dynamic pressure are captured in one cell without smearing or oscillations along a multimaterial interface. A time-accurate incompressible Navier-Stokes/Euler solver is developed based on a three-point backward difference formula for the physical time marching. Artificial compressibility is introduced with respect to pseudotime and an implicit method is used for the pseudotime iteration. To track evolution of an interface, a level set function is coupled with the governing equations. Roe's flux difference splitting method is used to calculate numerical fluxes of the coupled equations. To get higher order accuracy, dependent variables are reconstructed based on gradients which are calculated using Gauss theorem. For each edge crossing an interface, dynamic pressure is assigned for a ghost node to enforce the continuity of total pressure along the interface. Solitary internal waves are computed and the results are compared with other computational and experimental results.

Moving Estimates Test for Jumps in Time Series Models

  • Na, O-Kyoung;Lee, Seon-Joo;Lee, Sang-Yeol;Choi, In-Bong
    • Communications for Statistical Applications and Methods
    • /
    • v.13 no.2
    • /
    • pp.205-217
    • /
    • 2006
  • In this paper, we consider the problem of testing for a change of the parameter function ${\theta}(t)$ that may have a discontinuity at some unknown point ${\tau}$. We introduce a varying-h moving estimate to test the null hypothesis that ${\theta}(t)$ is continuous against the alternative that ${\theta}({\tau}-){\neq}{\theta}({\tau}+)$. Simulation results are provided for illustration.

Investigation of the Finite Planar Frequency Selective Surface with Defect Patterns

  • Hong, Ic-Pyo
    • Journal of Electrical Engineering and Technology
    • /
    • v.9 no.4
    • /
    • pp.1360-1364
    • /
    • 2014
  • In this paper, RCS characteristics on defect pattern of crossed dipole slot FSS having a finite size have been analyzed. To analyze RCS, we applied the electric field integral equation analysis which applies BiCGSTab algorithm with iterative method and uses RWG basis function. To verify the validity of this paper, RCS of PEC sphere has been compared to the theoretical results and FSSs with defect patterns are fabricated and measured. As defect patterns in FSS, missing one column, missing some elements, and discontinuity in surfaces are simulated and compared with the measurement results. Resonant frequency shifts in pass band and changes in bandwidth are observed. From the results, precisely predicting and designing frequency characteristics over defect patterns are essential when applying FSS structures such as FSS radomes.

Extended MLS Difference Method for Potential Problem with Weak and Strong Discontinuities (복합 불연속면을 갖는 포텐셜 문제 해석을 위한 확장된 MLS 차분법)

  • Yoon, Young-Cheol;Noh, Hyuk-Chun
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.24 no.5
    • /
    • pp.577-588
    • /
    • 2011
  • This paper provides a novel extended Moving Least Squares(MLS) difference method for the potential problem with weak and strong discontinuities. The conventional MLS difference method is enhanced with jump functions such as step function, wedge function and scissors function to model discontinuities in the solution and the derivative fields. When discretizing the governing equations, additional unknowns are not yielded because the jump functions are decided from the known interface condition. The Poisson type PDE's are discretized by the difference equations constructed on nodes. The system of equations built up by assembling the difference equations are directly solved, which is very efficient. Numerical examples show the excellence of the proposed numerical method. The method is expected to be applied to various discontinuity related problems such as crack problem, moving boundary problem and interaction problems.