Extraction of ritz vectors from vibration test data

摘要

Modal parameters obtained from modal testing (such as modal vectors, natural211u001efrequencies, and damping ratios) have been used extensively in system 211u001eidentification, finite element model updating, and structural health monitoring. 211u001eAs an alternative to modal vectors, load-dependent Ritz vectors have been shown 211u001euseful in various areas of structural dynamics such as model reduction and damage 211u001edetection. The applications of Ritz vectors, however, have been mainly limited in 211u001eanalytical and numerical analyses because of the difficulty to identify them from 211u001evibration tests. This paper presents a procedure to extract load-dependent Ritz 211u001evectors using a complete flexibility matrix constructed from measured vibration 211u001etest data. The proposed method can not only construct the Ritz vectors 211u001ecorresponding to the actual load pattern employed in vibration tests, but also 211u001egenerate Ritz vectors from arbitrary load patterns. Experimental data obtained 211u001efrom the vibration test of a grid-type bridge structure are employed to validate 211u001eand illustrate the proposed extraction procedure.