Wyniki wyszukiwania - BazTech

1

Experimental identification of modal parameters for the model of a building subjected to short-term kinematic excitation

Majcher K.

Studia Geotechnica et Mechanica

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2018

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Vol. 40, nr 4

321--332

EN

In this work, the input-output method of dynamic parameters’ identification is experimentally tested. A method based on the transformation of a dynamic problem into a static problem by means of integration of the input and output signal was presented. The problem discussed in this article is the identification of the coefficients of stiffness matrices and eigenfrequencies of a discrete dynamic system subjected to kinematic input. The experimental analysis was carried out on a three-storey slab-and-column structure, which constitutes a physical model of a building. The vibrations of the model were excited kinematically by an earthquake simulator. The device has a computer-controlled, movable table top, which can move independently in three directions, that is, horizontally, vertically, and rotationally around the vertical axis. The aim of the experimental studies presented in this work was to determine the dynamic parameters of the model (stiffness, natural frequencies) using the input-output method in the time domain. Moreover, the results obtained with this method were compared with the results of experimental modal analysis (EMA) in order to verify their correctness. It was assumed that the movement of the base is horizontal and occurs in one direction. Two short-term, irregular kinematic excitations of the construction were considered, and the selected results and conclusions from experimental analyses were presented in this work.

2

Experimental research of cable tension tuning of a scaled model of cable stayed bridge

Pakos W., Wójcicki Z., Grosel J., Majcher K., Sawicki W.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 1

41--52

EN

The paper describes the idea and the algorithms of a method for reducing the resonant vibration of the cables in a footbridge. The method relies on change of the static tension in chosen cables of the footbridge. The changes in static tension are introduced when resonance vibration occurs. The paper delineates empirical research employed to experimentally verify the numerical prediction. It has been demonstrated that it is possible to select some stay cables in which applicable change in static tension force value ensures amplitude reduction of forced resonance oscillations of any cable of the whole system. The choice of cables and the magnitude of tension change in them were based on the sensitivity analysis of an eigenproblem formulated in accordance with second order theory. The experimental research was designed to demonstrate practical effectiveness of amplitude reduction of stay cable resonant vibration method. A physical laboratory model of the footbridge was built in compliance with dimensional analysis on a scale of 1:10. Operational Modal Analysis (OMA) method was applied to identifying modal characteristic of a footbridge model.

3

Analiza numeryczna stateczności dynamicznej belki swobodnie podpartej z ciągłym rozkładem masy

Majcher K.

Inżynieria i Budownictwo

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2015

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R. 71, nr 12

664--666

PL

Przedstawiono kombinowany algorytm bazujący na komercyjnych pakietach obliczeniowych COSMOS/M i MATHEMATICA, umożliwiający analizę skomplikowanych zagadnień teoretycznych mechaniki budowli, w których występuje problem zmiennych w czasie parametrów układu, np. właściwości geometryczno-materiałowych. Zamieszczono przykład takiej analizy.

EN

In this paper the combined algorithm based on two commercial systems (COSMOS/M and MATHEMATICA) is presented. The algorithm enables analyzing complex theoretical problems of structural mechanics, especially if the system parameters are time-dependent, e.g. geometric and material properties. The efficiency of the algorithm is verified by numerical analysis of dynamic stability problem of simply supported beam with continuous mass distribution.

4

Kinematically excited parametric vibration of a tall building model with a TMD - Part 1: Numerical analyses

Majcher K., Wójcicki Z.

Archives of Civil and Mechanical Engineering

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2014

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Vol. 14, no. 1

204--217

EN

This paper undertakes to analyze the research problem of vibration of a tall building with a Pendulum Tuned Mass Damper (PTMD). The vibration of the building-damper system is due to kinematic excitation representing seismic load. It was assumed that during an earthquake the ground can move horizontally and vertically. An analysis of various earthquakes reveals that, sometimes, the vibration has comparable amplitudes in both these directions. It is usually the horizontal vibration that is catastrophic to structures. Vertical vibration is therefore often omitted. As this paper will show, in cases where the TMD model is a pendulum, the vertical ground motion can be transmitted through the building structure to the pendulum suspension point. In such cases, parametric resonance may occur in the system, which is especially dangerous as it amplifies vibration despite the presence of damping. Taking this phenomenon into consideration will make it possible to better secure the structure against earthquakes. As the teams carrying out theoretical and experimental analyses differed, the paper was purposely divided into two parts. In the first part, the idea was formulated and the MES model of the building-TMD system was created. The second part contains an experimental verification of the theoretical analyses.

5

Kinematically excited parametric vibration of a tall building model with a TMD - Part 2: Experimental analyses

Majcher K., Wójcicki Z., Grosel J., Pakos W., Sawicki W.

Archives of Civil and Mechanical Engineering

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2014

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Vol. 14, no. 1

218--229

EN

This paper constitutes the second part of the article Kinematically excited parametric vibration of a tall building model with a TMD. Part 1: numerical analyses (ACME, in press) by K. Majcher and Z. Wójcicki, which presents the results of theoretical research. This paper presents the experimental verification of those results. The experimental studies were carried out with the use of an especially designed physical model of a tall building, which rested on an earthquake simulator – a shaking table – created for this project. The simulator was used to generate several types of kinematic excitations: harmonic ones, superpositions of harmonic ones and, finally, ones generated on the basis of real seismograms. Vibrations were kinematically excited in the horizontal and vertical directions independently and simultaneously. The vertical component of the earthquake causes the pendulum suspension point to vibrate, thus exciting the pendulum parametrically. The theoretical study indicated a significant influence of this parametric excitation (parametric resonance) on the effectiveness of the Pendulum Tuned Mass Damper (PTMD). Therefore, the experimental analyses were especially focused on the parametric effects' impact on: the PTMD's ability to reduce the building's vibration, and the possibility of parametric resonance of the building due to parametric resonance of the PTMD.

6

Eksperymentalna i teoretyczna analiza dynamiczna konstrukcji

Wójcicki Z., Grosel J., Sawicki W., Majcher K., Pakos W., Brząkała A.

Inżynieria i Budownictwo

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2010

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R. 66, nr 12

706-709

PL

Opisano aparaturę do pomiarów dynamicznych wielkich konstrukcji inżynierskich i budowlanych. Przedstawiono przykłady jej wykorzystania do dynamicznych analiz różnych konstrukcji i modeli fizycznych. Stwierdzono, że w analizie konstrukcji inżynierskich i budowlanych powinny być jednocześnie prowadzone analizy teoretyczne i eksperymentalne w celu weryfikacji i walidacji modeli MES.

EN

Especially was presented an equipment for nondestructive research i.e. system for dynamic measurements of giant engineering structures. In paper is also some illustrative examples of usage of this system to dynamical analysis of different structures and models of structures. The authors propose that a new approach become the recommended standard in the analysis of engineering and building structures. According to them, both theoretical and experimental research should be carried out simultaneously in order to verify and validate FEM models.

7

Badanie drgań dużej konstrukcji przemysłowej

Wójcicki Z., Grosel J., Mironowicz W., Sawicki W., Brząkała A., Majcher K., Pakos W.

Materiały Budowlane

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2009

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nr 3

132-136

8

Assessment of Metabolite Concentrations Changes in Rat Brain after Intravenous CDPcholine Injection Using Magnetic Resonance Spectroscopy in vivo

Kulinowski P., Labak M., Majcher K., Herbik A., Grieb P., Jasiński A.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 7

1125-1132

EN

CDPcholine (citicoline, CDPCho) shows beneficial effects in various Central Nervous System (CNS) injury models and neurodegenerative diseases. Previous studies demonstrate conflictingMagnetic Resonance Spectroscopy (MRS) reports regarding the impact of different choline-containing compounds and its doses on brain metabolites. This preliminary study was designed to evaluate concentration changes of brain MR-visible metabolites following intravenous CDPCholine. Twelve healthy rats treated with CDPCholine in three subsequent doses of 1gram/kg eachwere examined using 1Hand 31P MRS in vivo. Following intravenous CDPCholine administration there was a statistically significant increase of the Cho/Cr ratio after first CDPCholine injection. The evidence of CDPcholine influence on brain metabolites has been shown.