Odd Tullberg

A framework for immersive FEM visualisation using transparent object communication in a distributed network environment

We present the implementation of a software framework for conducting interactive FE simulations within Virtual Environments (VEs), and show how this can be used for the visualisation of loading on large-scale structures. Approximation methods that allow results to be displayed within the VE before the FEA is complete are also discussed. The framework is built using modular object orientated technology, and exists as a distributed application running over a WAN. Use of modern distributed object libraries allows this parallelism to be largely transparent within the framework. The use of strictly enforced software interfaces provides a clean separation between our framework and the modules that provide services and functionality.

BEMSTAT — A New Type of Boundary Element Program for Two-Dimensional Elasticity Problems

A new type of boundary element program is presented. The equations are derived by use of integral operators. A natural way of deducing element matrices in BEM is shown, which leads to a new technique for establishing the system of equations. A simple subsidiary condition technique, which makes it possible to take discontinous tractions into account, is presented. Guidelines are given for the BE-discretization and the numerical integration. Formulas for the analytical integration of the singular terms are shown. A non-conventional method for coupling BEM and FEM is proposed. Numerical studies have been made in order to investigate the performance of different elements.

Boundary element method applied to two-dimensional heat conduction in non-homogeneous media

Abstract The boundary element method applied to two-dimensional heat conduction in homogeneous and non-homogeneous media has been studied. A computer program using linear approximations for both the temperature and flux and where the flux is permitted to have jumps in the nodes has been developed. A method for direct establishment of the final system of equations, also for the non-homogeneous case, is presented. This method reduces the computer time and storage area. Ordinary boundary conditions, i.e. prescribed temperature and prescribed flux, can be taken into account as well as conditions for boundaries with convection. Several numerical examples are given and comparison with both analytical solutions and FEM solutions have been made, demonstrating the accuracy of the program.

Dynamic soil structure interaction problem including viscous damping

A boundary element solution procedure is given for dynamic soil-structure interaction problem including viscous damping. The boundary integral equation of elastodynamics and the relationship of viscoelastic-elastic analogy (the correspondence principle) are established through the use of the Laplace transform. Thus the problem of viscous damping can be solved numerically in the same manner as the elastodynamic case without damping. Examples of soil structure interaction including viscous damping under harmonic external force is computed and compared with no damping. Also, dynamic interaction between adjacent foundation are studied for different distancies and frequencies.