STUDY OF DAMAGE IDENFICATION METHOD BASED ON THE COVARIANCE OF STRAIN IMPULSE RESPONSE FUNCTION

Structural damage identification based on vibration characteristics is the research topic in civil engineering in recent years. When the structure is damaged, the stress of the surrounding damage part of the structure will be redistributed obviously and the strain will have distinct change. So the damage detection can be performed by the comparison of the strain or the parameter from the strain responses between the damaged and intact states of the structure. In this paper the covariance of strain impulse response function (CoS) is proposed and it is proved that CoS is the function of structural modal parameters. It is the energy integral of the strain impulse response on the time interval. Compared to the traditional modal parameters, more high modes of modal parameters are preserved in the CoS and the errors produced in the modal parameter identification procedure are avoided. So the CoS can be used for structural damage identification. A simplysupported steel beam is studied to demonstrate the performance of CoS in the damage identification. From the results of numerical studies, it can be found that CoS can identify damage occurrence and location successfully. Moreover, any analytical structural model is not necessary for the damage identification procedure based on CoS. Only the computation or measurement of the strain response, strain impulse response function and CoS from the intact and the damaged states of the structure is required. It means that CoS is very suitable for health monitoring of real engineering structures.