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1
Content available The use of modal analysis to examine the lattice structure
Żółtowski Mariusz, Jeleniewicz Katarzyna
Przegląd Naukowy Inżynieria i Kształtowanie Środowiska
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2019
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Vol. 28, No. 3
332--344
EN
Steel structures are subject to large dynamic loads clearly reflected by generated vibration processes. The vibrations may affect state of serviceability of structures by lowering comfort of persons working there as well as possible reaching the level hazardous to safety of the structures. The effect of vibrations to structure is mainly manifested by additional stresses in a given cross-section, which are summed up with those resulting from static loads. The dynamic loads may cause damaging effects in buildings of various structural types or even lead to their destruction. Judging the necessity of improving the quality assessment methods of building structures for purposes of estimation of their state as well as safety factors for lattice structures, the author of this work undertook an attempt to investigate destruction process of selected object by using the modal analysis method.
2
Content available Numerical models for the evaluation of natural vibration frequencies of thermo-modernized building walls
Kuźniar K., Zając M.
Archives of Civil Engineering
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2018
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Vol. 64, nr 4/I
3--14
EN
As a result of the necessity to improve energy properties of prefabricated buildings, their thermo-modernizations are performed. In the paper various approaches to the modelling of prefabricated load bearing walls before and after thermo-modernization are presented. Simple one layer models with extra mass from ceilings and equivalent stiffness as well as multilayer ones are taken into consideration using the finite element method software. Values of the natural frequencies of the wall horizontal vibrations calculated using the various models, are compared. It was proved that even the very simple model with equivalent stiffness allows to compute natural vibration frequencies of wall with acceptable accuracy for engineering practice.
PL
W niniejszej pracy pokazano różne podejścia do modelowania prefabrykowanych ścian nośnych przed i po termomodernizacji. Wykorzystując metodę elementów skończonych rozważono proste, jednowarstwowe modele o zastępczej sztywności oraz modele wielowarstwowe. Porównywano częstotliwości ich poziomych drgań własnych. Rozważono wysoką, typową prefabrykowaną ścianę nośną systemu budownictwa prefabrykowanego WWP – 10.8m szerokości i 29.7m (11 kondygnacji x 2.7m) wysokości. Każda płyta prefabrykowana składa się z trzech warstw: nośnej, izolacji cieplnej i elewacyjnej. Dodatkowe warstwy wynikające z termomodernizacji tworzą: zbrojona zaprawa, styropian i siatka z włókien szklanych.
3
Content available Investigations of harbour brick structures by using operational modal analysis
Żółtowski M.
Polish Maritime Research
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2014
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nr 1
42--53
EN
Historic harbour brick objects are subject to large dynamic loads clearly reflected by generated vibration processes. The vibrations may affect state of serviceability of structures by lowering comfort of persons working there as well as possible reaching the level hazardous to safety of the structures. The effect of vibrations to structure is mainly manifested by additional stresses in a given cross-section, which are summed up with those resulting from static loads. Moreover often occur consequences associated with environmental conditions and fatigue of materials which accelerate destruction of the objects. Therefore the dynamic loads may cause damaging effects in buildings of various structural types or even lead to their catastrofic destruction. Judging the necessity of improving the quality assessment methods of building structures for purposes of estimation of their state as well as safety factors for brick structures (see PN-B- 03002 standard, p.3.1.3 and 4.6), the author of this work undertook an attempt to investigate destruction process of selected building structures by using the method of operational modal analysis.
4
Content available Optimal design of bar structures with their supports in problems of stability and free vibrations
Bojczuk D., Rębosz-Kurdek A.
Journal of Theoretical and Applied Mechanics
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2014
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Vol. 52 nr 2
533--546
EN
The problem of maximization of the buckling load and the problem of maximization of the natural vibration frequency under a condition imposed on the global cost is discussed. Cross-sectional areas of bar structures and number of elastic supports, their positions and stiffnesses (or the number and positions of rigid supports) are selected as design parameters. The proposed here algorithm of optimization of bar structures with their supports is applied for analysis of some optimization problems. Illustrative examples confirm applicability of the proposed approach.
5
Content available Damping of torsional vibrations of ship engine crankshafts – general selection methods of viscous vibration damper
Chomik W.
Polish Maritime Research
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2011
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nr 3
43-47
EN
This paper describes causes of torsional vibrations generated in ship engine crankshafts. Means for damping the torsional vibrations as well as general methods for selection of viscous torsional vibration dampers for a given type of engine are also presented. Exemplary results of calculations connected with selection of a viscous torsional vibration damper intended for a six-cylinder engine, are attached.
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