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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Computational Structural Engineering Institute of Korea
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Journal DOI :
The Computational Structural Engineering Institute
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Volume & Issues
Volume 27, Issue 6 - Dec 2014
Volume 27, Issue 5 - Oct 2014
Volume 27, Issue 4 - Aug 2014
Volume 27, Issue 3 - Jun 2014
Volume 27, Issue 2 - Apr 2014
Volume 27, Issue 1 - Feb 2014
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Level Set Based Topological Shape Optimization Combined with Meshfree Method
Ahn, Seung-Ho ; Ha, Seung-Hyun ; Cho, Seonho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 1~8
DOI : 10.7734/COSEIK.2014.27.1.1
Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.
Level Set Based Shape Optimization of Linear Structures using Topological Derivatives
Yoon, Minho ; Ha, Seung-Hyun ; Kim, Min-Geun ; Cho, Seonho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 9~16
DOI : 10.7734/COSEIK.2014.27.1.9
Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The "Hamilton-Jacobi(H-J)" equation and computationally robust numerical technique of "up-wind scheme" lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H-J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes are not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.
Analysis of Dynamic Crack Propagation using MLS Difference Method
Yoon, Young-Cheol ; Kim, Kyeong-Hwan ; Lee, Sang-Ho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 17~26
DOI : 10.7734/COSEIK.2014.27.1.17
This paper presents a dynamic crack propagation algorithm based on the Moving Least Squares(MLS) difference method. The derivative approximation for the MLS difference method is derived by Taylor expansion and moving least squares procedure. The method can analyze dynamic crack problems using only node model, which is completely free from the constraint of grid or mesh structure. The dynamic equilibrium equation is integrated by the Newmark method. When a crack propagates, the MLS difference method does not need the reconstruction of mode model at every time step, instead, partial revision of nodal arrangement near the new crack tip is carried out. A crack is modeled by the visibility criterion and dynamic energy release rate is evaluated to decide the onset of crack growth together with the corresponding growth angle. Mode I and mixed mode crack propagation problems are numerically simulated and the accuracy and stability of the proposed algorithm are successfully verified through the comparison with the analytical solutions and the Element-Free Galerkin method results.
Analytical Study on Effect of Floor Slab for Progressive Collapse Resistant Capacity of Steel Moment Frames
Kim, Seonwoong ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 27~35
DOI : 10.7734/COSEIK.2014.27.1.27
In this study, an improved energy-based nonlinear static analysis method are proposed to be used for more accurate evaluation of progressive collapse potential of steel moment frames by reflecting the contribution of a double-span floor slab. To this end, the behavior of the double-span floor slab was first investigated by performing material and geometric nonlinear finite element analysis. A simplified energy-absorbed analytical model by idealizing the deformed shape of the double-span floor slab was developed. It is shown that the proposed model can easily be utilized for modeling the axial tensile force and strain energy response of the double-span floor slab under the column-removal scenario.
A Variational Numerical Method of Linear Elasticity through the Extended Framework of Hamilton's Principle
Kim, Jinkyu ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 37~43
DOI : 10.7734/COSEIK.2014.27.1.37
The extended framework of Hamilton's principle provides a new rigorous weak variational formalism for a broad range of initial boundary value problems in mathematical physics and mechanics in terms of mixed formulation. Based upon such framework, a new variational numerical method of linear elasticity is provided for the classical single-degree-of-freedom dynamical systems. For the undamped system, the algorithm is symplectic with respect to the time step. For the damped system, it is shown to be accurate with good convergence characteristics.
Experimental Study and Evaluation of Tension Stiffening Model in High Strength Concrete Beams
Shin, Dae Hwan ; Jo, Eunsun ; Kim, Min Sook ; Kim, Heechuel ; Lee, Young Hak ;
Journal of the Computational Structural Engineering Institute of Korea, volume 27, issue 1, 2014, Pages 45~53
DOI : 10.7734/COSEIK.2014.27.1.45
In strength limit states design, it is assumed that after cracking, reinforcement carries all tension in the tension zone of reinforced concrete members. However, it can be seen the concrete between cracks will contribute to carrying a part of the tension stress in actual concrete members particularly at service load levels, this effect is referred as tension stiffening effect. In this study, tension stiffening models and high strength concrete beam flexural test results were verified through comparison. The relationship between moment-curvature and load-deflection was evaluated by result of tension stiffening model and test result values. The analysis results showed that ACI 318 and Owen & Damjanic generally shows good agreement.