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Blachowski B.D.,Polish Institute of Fundamental Technological Research | Gutkowski W.,Institute of Mechanized Construction and Rock Mining | Wisniewski P.,Polish Institute of Fundamental Technological Research
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

The paper deals with a nonlinear analysis of a tall tower, with Circular Flange Bolted Connections (CFBC), in which friction and contact effects are taken into account. Due to these nonlinearities, a detailed dynamic model of the whole structure would lead to very complex computational problem, unable for practical solutions. To overcome these difficulties a reduced order model of CFBC is proposed. Such a model enables the simulation of the whole tower including nonlinearities in connections. The paper is illustrated with an example of model reduction and dynamic calculations for a contemporary telecommunication tower. The tower is assembled of 4 truss segments, of triangular cross section, interconnected with CFBCs. Finally, the influence of the number of modes, included in the reduced order model, on the accuracy and computational effect, is discussed.

Blachowski B.,Polish Academy of Sciences | Gutkowski W.,Institute of Mechanized Construction and Rock Mining
Bulletin of the Polish Academy of Sciences: Technical Sciences | Year: 2014

In this study, a relatively simple method of discrete structural optimization with dynamic loads is presented. It is based on a tree graph, representing discrete values of the structural weight. In practical design, the number of such values may be very large. This is because they are equal to the combination numbers, arising from numbers of structural members and prefabricated elements. The starting point of the method is the weight obtained from continuous optimization, which is assumed to be the lower bound of all possible discrete weights. Applying the graph, it is possible to find a set of weights close to the continuous solution. The smallest of these values, fulfilling constraints, is assumed to be the discrete minimum weight solution. Constraints can be imposed on stresses, displacements and accelerations. The short outline of the method is presented in Sec. 2. The idea of discrete structural optimization by means of graphs. The knowledge needed to apply the method is limited to the FEM and graph representation. The paper is illustrated with two examples. The first one deals with a transmission tower subjected to stochastic wind loading. The second one with a composite floor subjected to deterministic dynamic forces, coming from the synchronized crowd activities, like dance or aerobic.

Golos K.,Warsaw University of Technology | Jastrzebski M.,Institute of Mechanized Construction and Rock Mining
Solid State Phenomena | Year: 2016

In the paper an extended experimental study and numerical analysis of fatigue strength of aluminum alloy EN AW – 6063 welded thin-walled aluminum structural stair construction is presented. The FEM calculations were carried out. In analysis the concept of the weak link was applied. The critical thin-walled welded tread stairs node was selected and the concept was verified experimentally for two variants of cyclic loading. The effect of cyclic loading on crack initiation and propagation in the welds and residual strength was examined. It was observed the reduction in residual strength, i.e. 1.61% for the construction of thin-walled welded connection after 30 000 cycles, and about 6.19% after 100 000 cycles. © 2016 Trans Tech Publications, Switzerland.

Blachowski B.,Polish Institute of Fundamental Technological Research | Swiercz A.,Polish Institute of Fundamental Technological Research | Gutkiewicz P.,Polish Institute of Fundamental Technological Research | Szelazek J.,Polish Institute of Fundamental Technological Research | Gutkowski W.,Institute of Mechanized Construction and Rock Mining
Measurement: Journal of the International Measurement Confederation | Year: 2016

An experimental and analytical study of the relation between local defect, in a steel structure, and its higher frequencies and higher modes is discussed. The structure is a plane steel frame, assembled of beams, joined together with bolted connections. Removing some bolts from a given connection simulates the damage. In the experiment, an impulse force induced structural vibrations. Effects of vibrations were shown by data from gages, measuring accelerations with a high accuracy. From the data, it could be observed, that mode shapes, for the healthy and damaged structures didn't show any differences for low frequencies. Only modes around thirteen showed significant gap between picks of Frequency Response Functions, for healthy and damaged frame. Moreover, looking at mode shapes, it could be observed that structural configuration may have some influence on defects to be observable. This aspect is discussed in a separate section. The experiment performed on the whole structure allows finding the place where the defect is localized. However, it can't give detailed information on the defect itself, here defect of a bolt. For finding it, an ultrasonic measurement of pre-tensioning forces in bolts was applied. It allowed not only to determine stresses in the bolt, but also to verify, if in the process of assembling the structure was not pre-stressed. © 2016 Elsevier Ltd. All rights reserved.

Smiszek-Lindert W.,Institute of Mechanized Construction and Rock Mining | Michta A.,University of Silesia | Tyl A.,University of Silesia | Malecki G.,University of Silesia | And 2 more authors.
Journal of the Serbian Chemical Society | Year: 2015

The X-ray structure, theoretical calculation, Hirshfeld surfaces analysis, IR and Raman spectra of fluoranthene and acenaphthene were reported. Acenaphthene crystallizes in the orthorhombic crystal system and space group P21ma, with crystal parameters a = 7.2053(9) Å, b = 13.9800(15) Å, c = = 8.2638 (8) Å, Z = 4 and V = 832.41(16) Å3. In turn, the grown crystals of fluoranthene are in the monoclinic system with space group P21/n. The unit cell parameters are a = 18.3490(2) Å, b = 6.2273(5) Å, c = 19.8610(2) Å, ß = = 109.787(13)°, Z = 8 and the unit cell volume is 2135.50(4) Å3. Theoretical calculations of isolated molecules of the title compounds were performed using DFT at the B3LYP level. The intermolecular interactions in the crystal structure, for both the title polycyclic aromatic hydrocarbons were analyzed using the Hirshfeld surfaces computational method. © 2015 SCS.

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