EARLY STRUCTURAL DAMAGE ASSESSMENT BY USING AN IMPROVED FREQUENCY EVALUATION ALGORITHM

Abstract

THIS PAPER INTRODUCES A METHOD TO IDENTIFY DAMAGES IN BEAM-LIKE STRUCTURES BY ANALYZING THE NATURAL FREQUENCY CHANGES OF THE FIRST SIX TRANSVERSAL VIBRATION MODES. A CORRELATION BETWEEN THE DAMAGE LOCATION AND FREQUENCY CHANGE IS ESTABLISHED FOR EACH MODE SEPA-RATELY, BY CONSIDERING THE MODAL STRAIN ENERGY STORED IN THAT LOCA-TION. THE MATHEMATICAL RELATION DESCRIBING THIS CORRELATION IS USED TO CHARACTERIZE THE DYNAMIC BEHAVIOR OF A BEAM WITH A DAMAGE OF KNOWN POSITION AND TO DERIVE ITS DAMAGE LOCATION INDICATOR (DLI) AS A SIX-TERM VECTOR. THE METHOD CONSISTS IN COMPARING THE VEC-TORS DESCRIBING THE DAMAGE AT ANY POSSIBLE LOCATION ALONG THE BEAM WITH THE DAMAGE SIGNATURE (DS), WHICH IS ACHIEVED FROM THE MEASUREMENTS THAT COMPARE THE BEAMÂS FREQUENCIES IN HEALTHY AND DAMAGED STATE. A MODIFIED KULLBACK-LEIBLER DIVERGENCE IS USED TO ASSESS THE DAMAGE LOCATION. IN ORDER TO PERMIT EARLY DAM-AGE ASSESSMENT, AN IMPROVED FREQUENCY EVALUATION ALGORITHM WAS DEVELOPED. IT IS BASED ON SIGNAL TRUNCATION AND CONSEQUENT SPECTRAL LINES REARRANGEMENT, IN ORDER TO ACCURATELY FIND THE STRONGEST SPECTRAL COMPONENTS. THE EFFECTIVENESS OF THE PROPOSED METHOD IS DEMONSTRATED BY SIMULATIONS AND EXPERIMENTS.