Ivan Němec

Ivan Němec
Technical University Brno

Assoc. Prof., Ing., PhD.

About

27
Publications
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47
Citations

Publications

Publications (27)
Conference Paper
The paper deals with complex nonlinear time-dependent material models used in a structure exposed to fast dynamic loading. The finite element solution with the use of the explicit method for the direct integration of equations of motion is provided. Two material models suitable for description of nonlinear response of structure to dynamic loading w...
Conference Paper
This paper presents an approach for a weld connection modeling in the finite element method using the method of La-grange multipliers. The key issue is to fulfil contact conditions of the weld connection with the possibility to use it for connection of non-conforming meshes. That is why a general node-to-segment (NTS) algorithm which enables to def...
Article
Advanced numerical analysis of structures forces the massive implementation of numerical algorithms, relying on certain convergence of sequences of discrete finite element and similar approximations in spaces of integrable functions, conceding non-physical discontinuities and imperfectness to all numerical results. This is demonstrated on a model e...
Conference Paper
Improved stability of the node-to-node (NTN) algorithm gained by modification of the algorithm with regard to the explicit method is presented in this paper in order to enable fast and precise analysis of models containing NTN contacts in structural dynamics using Finite Element Method. The key issue is to fulfil contact conditions and prevent solu...
Conference Paper
The paper deals with suitability of use of the explicit and implicit method in heavily nonlinear seismic analysis and also deals with comparison of response of the Drucker-Prager plastic material model and the modified Mazars damage material model to strong seismic loading. Considering typical time of duration of earthquakes from several seconds to...
Article
Full-text available
The paper deals with suitability of use of the explicit and implicit method in heavily nonlinear seismic analysis. Considering typical time of duration of earthquakes from several seconds to approximately twenty seconds, it would seem that use of the implicit method is definitely more suitable. The shape of accelerograms, however, requires quite sh...
Article
Full-text available
In this paper, the form of modifications of the existing sequential code written in C or C++ programming language for the calculation of various kind of structures using the explicit form of the Finite Element Method (Dynamic Relaxation Method, Explicit Dynamics) in the NEXX system is introduced. The NEXX system is the core of engineering software...
Article
Full-text available
The cable-pulley system is widely used for its advantages. In this paper, application of a new algorithm for the calculation of cables on pulleys is presented. Unlike other algorithms, this algorithm enables to take the magnitude of the radius of each pulley into account. This new algorithm is implemented in the RFEM program because of its higher a...
Article
This paper introduces a procedure for parallel computing with the Dynamic Relaxation method (DR) on a Graphic Processing Unit (GPU).This method facilitates the consideration of a variety of nonlinearities in an easy and explicit manner.Because of the presence of inertial forces, a static problem leads to a transient dynamic problem where the Centra...
Article
Full-text available
The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, and stability. For very large compressions, the tangent stiffness in the direction of the compression can even become negative, which c...
Article
The aim of this paper is an introduction to a very specific area of civil engineering, which is known as tensile structures (structures acting only in tension). These structures are associated with unique aspects of their design. As a result of practically zero bending stiffness, it is not possible to separate the shape and the static analysis of t...
Article
The aim of this contribution is a form-finding process. It is the problem of initial pre-stressed shape generation of membrane constructions. The contribution deals with specific aspects of this process and the necessity of introducing stabilization with regard to its practical application. Individual examples will show the results of methods descr...
Article
Full-text available
The subject of this article is the question of design and analysis of membrane structures. The first part of this article deals with the problem of form-finding. It is the problem of searching for the initial shape of membrane structure. In the second part of the article, an example of design and analysis of the membrane structure of a stadium roof...
Article
Full-text available
The presented article is a contribution to the discussion concerning nuclear safety which has intensified after the Fukushima Daiichi nuclear disaster. A parametric study concerning various materials, containment wall thicknesses and different aircraft speeds at the time of impact was performed. The aim of this study was to establish damage extent...
Article
The article deals with problems in designing and analyzing the membrane structure of a stadium roof. Attention is especially given to problems relating to the optimal design of the shape of the membrane (form finding) and the supporting cable system with respect to static behavior, functionality and architectural appearance. The work was carried ou...
Chapter
The program DEFOR can perform linear and geometrically nonlinear analysis of elastic, statically loaded structures composed of one-dimensional beam elements following the finite element analysis method. The elements can be of any technical type which can be represented by a centroidal axis and analysed as line elements. The structure can be compose...
Chapter
NE-XX is a general purpose elastic finite element program package for static structural analysis. It consists of ten programs for partial problems such as thin and thick plates, plane stress and plane strain, axisymmetrical stress, shells, shells with ribs of the other stiffeners, if needed in a generalized elastic medium, Saint Venant torsion, hea...
Article
Various solutions of laminated plates by the finite element method are analysed. An efficient solution of skew (or rectangular) laminated plates with small effect of σz and ϵz stress and strain components is developed. It can be used with an arbitrary number of layer elements (sub-elements) in different plate elements. Some remarks to the possible...

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