Detection of abrupt structural damage induced by an earthquake using a moving time window technique

This paper presents a time domain system identification (SI) scheme for detection of sudden structural damage that occurs during an earthquake. A moving time window technique is proposed to trace abrupt changes in the structural parameters caused by sudden damage. The time window represents a finite time interval, in which the SI procedures are performed assuming time-invariant system parameters. As the time window moves forward, the variation of system parameters in time is identified. The error function is defined as the time integral of the squared errors between measured accelerations and calculated accelerations by a mathematical model. Structural damping is approximated by the Rayleigh damping model, and damping properties as well as stiffness properties of a structure are considered as system parameters. A regularization technique is adopted to alleviate the ill-posed characteristics of SI problems. In the formulation of a new regularization function in time domain, a weighting factor is introduced to balance the relative regularization effect between stiffness and damping parameters. A truncated singular value decomposition scheme is applied to impose the regularization function on the minimization of the error function. Numerical simulation studies are presented to demonstrate the validity of the proposed method.