Suk Yoon Chang

Stress distributions of anisotropic three-dimensional semi-infinite bodies by a refined finite difference formulation

This paper deals with normal and shear stress distributions of anisotropic three-dimensional (3D) semi-infinite bodies using improved finite difference method (FDM). In the numerical analysis of various mechanical problems involving complex partial differential equations, the FDM has an advantage over the finite element method in its ability to avoid mesh generation and numerical integration. In this study, one of the important points in the finite difference formulation for 3D anisotropic problems is the generalized approach for various boundary conditions. A large number of studies in FDM have been made on clamped or simple boundary conditions by merely an energy approach. These approaches cannot be satisfied, however, with pivotal points along the free boundary. This study addresses the 3D problem of anisotropic semi-infinite bodies by adopting a refined 3D finite difference modeling elimination of pivotal difference points in the case of a free boundary condition. Moreover, the numerical examples present stress distribution characteristics through the depth direction of more complicated anisotropic semi-infinite bodies. The study also demonstrates the differences between the displacement and stress characteristics of isotropic, orthotropic and anisotropic cases.

Finite Difference Stress Analysis of Anisotropic Three-dimensional Curved Bodies with Free Boundaries

This paper investigates normal and shear stress distributions of anisotropic three-dimensional (3D) curved bodies using the Refined Finite Difference method (FDM). In the numerical analysis of various mechanical problems involving complex partial differential equations, the FDM has an advantage over the Finite Element Method in its ability to avoid mesh generation and numerical integration. One of the important points in the finite difference formulation for 3D anisotropic problems is the generalized approach for various boundary conditions. Many studies in FDM have been made on clamped or simple boundary conditions using merely an energy approach. These approaches cannot be satisfied, however, with pivotal points along the free boundary. This study addresses the 3D problem of anisotropic curved bodies by adopting a refined 3D finite difference modeling elimination of pivotal difference points in the case of a free boundary condition. Numerical examples present stress distribution characteristics through the depth direction of more complicated anisotropic curved bodies. The study also demonstrates the differences between the displacement and stress characteristics of isotropic, orthotropic and anisotropic cases.

Elastic Buckling Analysis of Laminated Composite Plates with Through-the-width Delamination Using EAS Solid Element

Delamination reduces an elastic buckling load of the laminated composite structures and lead to global structural failure at loads below the design level. Therefore, the problem of the delamination buckling of laminated composite structures has generated significant research interest and has been the subject of many theoretical and experimental investigations. However, questions still remain regarding a complete understanding and details of the phenomena involved. In this paper an efficient finite element model is presented for analyzing the elastic buckling behavior of laminated composite plates with through-the-width delamination using a solid element based on a three-dimensional theory. The solid finite element, named by EAS-SOLID8, is based on an enhanced assumed strain method. The study for elastic buckling behavior of laminated composite plates with through-the-width delaminations are focused on various parameters, such as size of delamination, support condition, aspect ratio, width-to-thickness ratio, stacking sequences, and location of delamination and multiple delaminations.

RETRACTED ARTICLE: Field testing and capacity-ratings of a short-span bridge superstructures made of advanced composite materials

Recently, there have been many theoretical and experimental studies on advanced composite materials (ACM) bridges in various fields over the world. Compared with a reinforced concrete or steel bridge, an ACM bridge has more advantages in strength, stiffness, transportation, and installation. Many demonstration projects have been carried out in the U.S, and Europe. They are also being developed and tested in South Korea. In South Korea the first of all ACM short-span bridge superstructures was installed on a public highway system in May 2002. Since these composite materials are new to bridge applications, reliable data is not available for their in-service performance. This paper describes in-service performance assessment of all ACM bridge superstructures. To investiga te its in-service performance, field load testing and visual inspections were conducted under an actual service environment. The p aper includes the presentation and discussion for ACM Bridge capacity rating based on the stress modification coefficients obtained from the test results. The test result indicates that the ACM bridge superstructure has no structural problems and is structurally performing well in-service as expected. The results may provide a baseline data for future field ACM bridge capacity rating assessments and also serve as part of a long-term performance of ACM bridge superstructure.