This paper deals with selection strategy of fixing nodes in the FETI-DP method. The FETI-DP method is one of non-overlapping domain decomposition methods. The method was published by Farhat and co-workers in 2001. Selection of the fixing unknowns in the FETI-DP, TFETI or BDDC domain decomposition method has strong influence on the method behavior. The selection itself is not straightforward in the case of irregular domains and subdomains. Three-step algorithm for the selection of the fixing unknowns is presented and some numerical examples are shown. The algorithm is based on nodal multiplicity, which is the number of subdomains sharing the node. If the three-step algorithm selects unsatisfactory number of fixing nodes, additional geometrical conditions are applied. These conditions lead to selection of additional fixing nodes. Moreover, higher number of the fixing nodes usually results in better convergence of the coarse problems.
Authors:Jaroslav Kruis, Tomáš Koudelka, and Tomáš Krejčí
This paper is devoted to efficient computer implementation of coupled salt and moisture transport processes. Three material models are summarized first and then a general form of coupled transport processes is formulated. The system of balance equations is solved numerically with the help of the Galerkin method (in space) and the generalized trapezoidal rule time integration. Implementation of the transport processes into the open source computer program SIFEL is briefly described.
The paper describes efficient methods to post-process results from the finite element analysis. Amount of data produced by the complex analysis is enormous. However, computer performance and memory are limited and commonly-used software tools do not provide ways to post-process data easily. Therefore, some sort of simplification of data has to be used to lower memory consumption and accelerate data loading. This article describes a procedure that replaces discrete values with a set of continuous functions. Each approximation function can be represented by a small number of parameters that are able to describe the character of resulting data closely enough.
Authors:Tomáš Krejèí, Tomáš Koudelka, and Jaroslav Kruis
This paper is devoted to a computer simulation of coupled-thermo-hydro mechanical analysis of concrete structures. The attention is concentrated to concrete structures at early stage, when hydration heat evolution and moisture content changes can influence significantly the reliability and service life of these structures. The results of computation are illustrated by the simulation of a foundation slab, which is situated in the basement of the administration building Prague-Tìšnov, Czech Republic. The Künzel and Kiessl approach is used to analyze heat and moisture fields and it is extended by a set of climatic conditions and by a model of hydration heat evolution in concrete. The problem is solved using the open source program SIFEL.