抗震Application of Dynamic System Identification to TimberBeams. I.pdfVIP

APPLICATION OF DYNAMIC SYSTEM IDENTIFICATION TO TIMBER BEAMS. I By S. T. Peterson,1 D. I. McLean,2 M. D. Symans,3 D. G. Pollock,4 W. F. Cofer,5 R. N. Emerson,6 and K. J. Fridley7 ABSTRACT: In this first part of a two-part paper, development of a method of dynamic system identification for timber beams is presented with an analytical verification of the method using a finite-element model. A method of global nondestructive evaluation for identifying local damage and decay in timber beams is investi- gated in this paper. Experimental modal analysis is used in conjunction with a previously developed damage localization algorithm. The damage localization algorithm utilizes changes in modal strain energy between the mode shapes of a calibrated model, representing the undamaged state of the beam of interest, and the experi- mentally obtained mode shapes for a timber beam. Analytical evaluations were performed to demonstrate and verify the use of this method of global nondestructive evaluation for the localization of damage or decay in timber beams. In a companion paper, experimental laboratory tests are presented that verify the use of dynamic system identification to locate damage within timber beams. INTRODUCTION in its modes of vibration and the response is measured at sev- eral points within the structure. Impulse excitation was se- Nondestructive evaluation (NDE) of wood is the science