Search results for "Modal analysis"
showing 10 items of 61 documents
Modal Analysis of a Reinforced Concrete Frame in Various States of Damage
2005
The purpose of this paper is to report selected results of an experiment in which two, natural size r/c frames were put on shaking table and subjected to a sequence of seismic excitations with increasing intensity interlaced with low level, diagnostic tests. The shaking table experiment aimed at working out new methodology for monitoring vibrations of r/c structures to assess their state. Characteristic decrease of natural frequencies and increase of structural damping was observed and analyzed in detail. It was interesting to note 20 per cent drop in natural frequencies prior to visual detection of any cracks.
Mode-superposition correction method for deterministic and stochastic analysis of structural systems
2001
The role played by the modal analysis in the framework of structural dynamics is fundamental from both deterministic and stochastic point of view. However the accuracy obtained by means of the classical modal analysis is not always satisfactory. Therefore it is clear the importance of methods able to correct the modal response in such a way to obtain the required accuracy. Many methods have been proposed in the last years but they are meaningful only when the forcing function is expressed by an analytical function. Moreover in stochastic analysis they fail for white noise excitation. In the paper a method able to give a very accurate response for both deterministic and stochastic input is p…
Stochastic response determination of structural systems modeled via dependent coordinates: a frequency domain treatment based on generalized modal an…
2019
Generalized independent coordinates are typically utilized within an analytical dynamics framework to model the motion of structural and mechanical engineering systems. Nevertheless, for complex systems, such as multi-body structures, an explicit formulation of the equations of motion by utilizing generalized, independent, coordinates can be a daunting task. In this regard, employing a set of redundant coordinates can facilitate the formulation of the governing dynamics equations. In this setting, however, standard response analysis techniques cannot be applied in a straightforward manner. For instance, defining and determining a transfer function within a frequency domain response analysis…
Efficient Low-Frequency Modal Analysis of Anechoic Chamber
2007
An efficient method to analyze the electromagnetic field inside rectangular anechoic and semianechoic chambers from 30 to 100 MHz is shown. A modal expansion is employed to develop the homogeneous and the inhomogeneous field. This is combined with circuital techniques to compute the effect of the layers of ferrite and dielectrics in the walls of the chamber. Several numerical results of the Free Space Transmission Loss (FSTL) of an anechoic chamber and the Normalized Site Attenuation (NSA) of a semianechoic chamber are provided.
The function of olfactory experience in reasoning : An empirical study
2019
This study reports the role of olfactory experience (i. e. smell of medication) in a nine-year old girl’s reasoning in pair-work situation where the children were asked to choose items useful on a desert island. The extract analysed here is part of the larger data set of my dissertation, in which I investigate how sensory-motor activities involved in reasoning. I video-recorded an experimental task, in which the participants (N=27; age=9; Hungarian L1) have been asked to choose 7 items out of 14 to take those to an imaginary uninhabited island. The multimodal analysis shows that children did not choose the vitamin pills due to its unpleasant smell. The findings suggests that crossmodal expe…
Designing an Innovative Face-Milling Cutter
2013
The paper consists in a research in the design of an innovative face-milling cutter, in terms of product lifecycle management (PLM), with the help from creative design methods, such as TRIZ. The model of the lifecycle management of the cutting tools was presented, emphasizing the functional analysis and creative design phase. Based on this analysis, a new constructive variant of the milling cutter was designed and simulated with finite element method, highlighting its advantages compared with classic construction variants.
Modal Analysis of Multi-Degrees-of-Freedom Systems with Singular Matrices: Analytical Dynamics Approach
2017
Complex mechanical (e.g., multibody) systems with different types of constraints are generally performed through analytical dynamics methods. In some cases, however, it is possible that the (augmented) mass and/or stiffness matrices may derive to be singular; consequently, modal analysis, which is used extensively in the classical dynamics literature, fails. In this paper, if the uniqueness condition is satisfied by the constraints, a properly modified modal analysis is elucidated into analytical dynamics leading to the evaluation of the natural frequencies in a simple and straightforward way. Under that framework, advances of both classical and analytical dynamics are taken into considerat…
Allocation of actuators and sensors for coupled-adjacent-building vibration attenuation
2013
An actuator and sensor allocation approach is proposed for the design of coupled-adjacent-building vibration suppression under seismic excitation. This paper first establishes a full-order model of adjacent buildings with the location information of actuators and sensors. Then, the order of the model is reduced via modal cost analysis, by retaining the modes contributing the most. In view of the fact that the output powers of the actuators are limited, this paper brings forward a mixed H∞/GH2 control. By considering that not all the states of the system can be measured by the sensors, a dynamic output feedback controller is designed. The genetic algorithm is employed to obtain the locations…
Fundamental period of infilled reinforced concrete frame structures
2016
AbstractThe fundamental period of vibration appears to be one of the most critical parameters for the seismic design and assessment of structures. In the present paper, the results of a large-scale analytical investigation on the parameters that affect the fundamental period of reinforced concrete structures are presented. The influence of the number of storeys, the number of spans, the span length, the infill wall panel stiffness and the percentage of openings within the infill panel on the fundamental period of infilled RC frames was investigated. Based on these results, a regression analysis is applied in order to propose a new empirical equation for the estimation of the fundamental per…
Efficient Analysis and Design Strategies for Evanescent Mode Ridge Waveguide Filters
2006
In this paper, a research on the compromises arisen in the design of traditional evanescent mode waveguide filters is carried out. As a result, clear design methodologies for optimizing length, losses, power handling and spurious-free out-of-band response are developed. In addition, an efficient and very accurate modal analysis tool for this kind of structures is presented. Several filters have been designed according to the different strategies proposed, and a prototype has been finally manufactured. Measurements and filter dimensions validate the proposed design procedures.