Experimental validation of an ambient vibration-based multiple damage identification method using statistical modal filtering

摘要

For civil engineering structures, ambient vibration tests are preferred over forced vibration ones because the artificially excitation of large structures having low natural frequencies is quite difficult and expensive. In the ambient vibration tests, operation disturbances can be avoided and the measured response is representative of the actual operating conditions of the structures which vibrate due to natural excitation. The proposed damage identification method is intended for moderate degrees of damage and requires vibration data relative to the current and reference states of the structure as well as a parametric finite element model. It is based on a residual generated from a modal filtering approach by the calculation of the error between the measurements at the current state and their projections onto the incomplete modal basis of the structure as identified at reference state. To detect and locate damage, the residual is evaluated by means of global, sensitivity and rejection tests, modified to allow only physically feasible simple and multiple damage scenarios. The mean of the residual, which turns out to be normally distributed, is used in the final phase of damage quantification. The proposed damage diagnosis method is validated experimentally via ambient vibration tests conducted on full-scale reinforced concrete beams and slabs which contain various simple and multiple damage configurations. With damage expressed in terms of loss of flexural stiffness, the damage detection, localization and quantification are found to be successful for degrees of damage less than about 28% of the initial flexural stiffness of the tested specimens. The exception is that, for multiple damage scenarios, the relative quantification errors may be unacceptable in locations where poor accuracy is expected.