Abstract. The experimental research results of material and geometrical characteristics of Czech steel are given in the presented paper. Measurements are carried out for the yield strength of plates made of steel grade S355. The values measured are used to compute axial resistances which are compared with the resistance resulting from standard (nominal) values. In this paper, there was used a statistical information for evaluating the results of strength measurements on a series of plates and hot-rolled profiles under tension to determine the adequate partial γ M0 safety factor.
Abstract. The presented paper deals with the stochastic analysis of the ultimate limit states of steel-concrete building members. The load carrying capacity of steel-concrete columns, comprising of steel profiles encased in high strength concrete, in compression is analyzed. The first part of the paper lists assumptions for the determination of the theoretical load carrying capacity of the column. Principles of elasticity and plasticity are used to determine stresses in the concrete and steel sections. Statistical characteristics of input material and geometrical imperfections are listed. Results of the theoretical analysis are then compared with results of experimental research. Statistical characteristics of obtained results of the theoretical analysis were verified using statistical characteristics obtained from experimental research. Numerical simulation LHS and Monte Carlo methods, which take into account the influences of variability of input imperfections, were employed. The influence of the utilization of the plastic reserve in the determination of the load carrying capacity of the analysed strut is shown. The influence of the initial geometric imperfections of initial strut curvature on the load carrying capacity is also presented.
ABSTRACT:The objective of the paper is to analyse the influence of initial imperfections on the behaviour of thin-walled girders welded of slender plate elements. The girder was modelled, using the geometrically and materially non-linear variant of the shell finite element method, by the ANSYS program. The ultimate static load-carrying capacity and the state of stress were considered as the output analysed quantities. The influence of the variability of initial imperfections on the variability of ultimate static load-carrying capacity and on the variability of the state of stress studied was calculated by sensitivity analysis. The sensitivity analysis was evaluated on a computer by applying the numerical simulation LHS method and statistical characteristics evaluated, based on the experiments. Real tests of girders with random initial imperfections the occurrence frequency of which is equivalent to experimental results are simulated numerically. In each LHS method run, both load-carrying capacity and state of stress are evaluated on the model based on nonlinear variant of shell finite elements. The stress state was evaluated by bending stresses developing in the crack-prone areas of a web "breathing" under repeated loads, which -as it was demonstrated by the experiments -occurred at the toes of the fillet welds connecting the "breathing" web with the girder flanges and stiffeners.
Sandwich panels supported by purlins are widely used as the main load bearing part of roof systems of steel buildings. Sandwich panels provide lateral and rotational restraint to purlins which positively influences their resistance. Lateral restraint given by sandwich panels is equal for both the downward and uplift loads applied on the panel's surface, though the rotational restraint may have different character. The uplift load reduces contact area between the panels and purlins which can result in smaller restraint value. ECCS Publication N o 135/CIB Publication 379 states, the rotational restraint for uplift shall be determined by tests with the recommended setup, otherwise a zero value has to be considered. The recommended setup, originally developed by Joachim Lindner, was also used for the large EASIE testing program which was the base of the aforementioned recommendation. The test setup from EN 1993-1-3, originally developed by Teoman Peköz for tests with cold-formed purlins and corrugated sheeting, has been considered as inappropriate for sandwich panels because it does not consider effects from transverse load. During the EASIE test program only hot-rolled purlins were tested and therefore evaluation did not take into account section distortion which is negligible for hot-rolled sections. The application of the test results for cold-formed purlins and conclusion related to the rotational restraint under uplift load therefore required re-confirmation by tests with cold-formed purlins. The experimental research, to determine the rotational restraint given to cold-formed Z purlins by sandwich panels, was performed at Brno University of Technology (BUT) in collaboration with Astron Buildings S.A. (Astron). Sandwich panels with direct fastening and hidden fastening, with PUR/PIR and mineral wool core were tested. ECCS/CIB test setup with the application of a torsional moment and a modified setup with the application of a direct force were used. Several tests were additionally done with the setup described in EN 1993-1-3. The creep effect was investigated as well. Based on the tests results, available test setups for cold-formed purlins were weighted and commented. The correction of the current draft of EN 1993-1-3 was proposed.
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