A Virtual Load Method for Damage Identification of Beam Structures

Abstract

Background: Damage identification at the earliest possible stage is very important for beam structures to ensure safety, extend serviceability, and reduce maintenance costs according to recent patents. Methods: The goal of this work is to develop a virtual load method for beam damage identification by using only the vibration modes of the current structure. Central to the damage identification approach is the construction of the virtual load according to the support conditions of the structure. A virtual quasistatic deformation of the structure can be obtained by multiplying its modal flexibility matrix with the virtual force vector. And then the possible damage location in the structure can be determined by sudden increases in curvatures of the virtual quasi-static deformation. Subsequently the damage extent can be simply computed if necessary. Results: Three types of beams are used as examples to demonstrate the efficiency of the presented virtual load method in structural damage identification. For comparison, damage localization was also conducted by the existing uniform load surface (ULS) curvature method. The results showed that the proposed virtual load method is applicable to all types of beams but the ULS curvature method is only applicable to the simple supported beam. Conclusion: It was found that the proposed method can successfully determine damage location and extent only using the partial modes of the current structure. Keywords: Damage identification, virtual load, vibration mode, beam structures, curvature, flexibility matrix.