STRUCTURAL DAMAGE DETECTION FROM INCOMPLETE AND NOISY MODAL TEST DATA

Existing research on structural damage detection usually requires info rmation at every degree of freedom, and this contradicts the usual pra ctice of having a small number of sensors employed over limited locati ons on the structure. A method to detect the location and to estimate the magnitude of damage in a structure down to the element level with incomplete and noisy measured modal data is proposed. The method consi sts of three stages: expansion of the measured mode shapes, localizati on of the damage domain using the elemental energy quotient difference , and damage quantification based on sensitivity of the modal frequenc y. A new mode shape expansion method is presented, and the effectivene ss of the combined use of this method and the elemental energy quotien t difference is demonstrated with incomplete measurement. The treatmen t of modeling errors is discussed. A criterion for selection of the da maged members is proposed and practical means to improve the identific ation results are presented. Several damage cases of the European Spac e Agency structure and of a single-bay two-story portal steel frame st ructure in the laboratory are investigated. The practical problem of h aving random error and systematic error in the measurement is studied. Results show that the proposed three-stage approach can effectively l ocate and quantify damages in a real structure.