Damage Identification of Beams Based on Improved Element Damage Variable with Reconstructed Modal Rotations

Abstract

Damage identification of structures is always attractive to researchers because it plays an important role in the health monitoring in many civil engineering structures. When carrying out a health monitoring, sensors are usually laid on a beam to record acceleration signals, in which the modes of the beam can be extracted to construct indicators for detecting damage of the investigated beam. It should be noted that it is difficult to measure rotational signals of the beam at a position where sensors are laid, thus only the modal translations are available. Although the modal translations can be used to construct indicators without modal rotations and often it is the case, an indicator taking into account modal rotations is suggested in application to resist the effect of noise on the accuracy of measurement. In this paper, modal rotations were reconstructed by modal translations using the principle of static condensation and QR decomposition. Then both modal translations and rotations were used to build an indicator based on element modal strain energy with the help of data fusion theory. The modal translations were extracted from accelerations recorded on a beam using stochastic subspace identification (SSI). Studies were carried out on choosing values of parameters in SSI in order to eliminate the effect of noise as nearly as possible. The simulation given by a FEM model and analyses of accelerations recorded on a reinforced concrete beam show that the proposed damage indicator with the efforts of eliminating noise is able to detect the locations of damage in the investigated beams.