“Computational Civil Engineering - "Intersections" International Journal

“Computational Civil Engineering 2005”, International SymposiumIaşi, România, May 27, 2005Single exciter techniques for structural identificationCristian-Claudiu Comisu1 Catedra Cai de Comunicatii si Fundatii, Facultatea de Constructii, Iasi, 70050, RomaniaSummaryThe main objective of structural identification is the development of an analyticalconceptualization of a structure, and quantifying, testing, improving, andvalidating the resulting analytical model by correlating responses simulated by themodel with those measured from the structure. The structural identificationrequires integrated analytical and experimental components of research orapplications.The experimental techniques can be further sub-divided into twocategories - single exciter techniques and multiple exciter techniques.This paper is focus to find an algorithm to quantify modal parametersobtained by the single exciter techniques. The advantages and disadvantages of thevarious exciter techniques will be discussed. The objectives of this paper are tointegrated analytical research (to find the mechanisms of flexibility, inertia anddamping that govern the dynamic responses) with the experimental components ofresearch (apply an algorithm to quantify modal parameters).The simplest and most commonly used technique is the peak amplitude method, inwhich the structure is excited by a sinusoidal force from a single exciter and theresponse curves of total amplitude, obtained at several points on the superstructureof bridge, are recorded as a function of frequency. Measurement of the excitingforce and the resulting motion at a number of points over a range of frequencieswould be sufficient to describe the vibrator behavior of the structure.The limitations of the peak amplitude method, when there are close resonances(which may be further aggravated by heavy damping) are summarized in thefollowing:1. A mode may be completely missed out;2. Errors may occur in estimation of damping and the principal modes;3. If the damping is very light experimental difficulties lie in makingmeasurements around the resonant frequencies.KEYWORDS: structural identification, exciter, analytical model, modalparameters, flexibility, inertia, damping