Element level structural damage detection with limited observations and with unknown inputs

In practical structural health monitoring, it is essential to develop an efficient technique which can detect structural local damage utilizing only a limited number of measured acceleration responses of structures subject to unknown (unmeasured) excitations inputs. In this paper, a finite-element based time domain system identification method is proposed for this purpose. Structure state vectors are treated as implicit functions of structural dynamic parameters and excitations. The unknown structural dynamic parameters and excitation inputs are identified by an algorithm based on recursive least squares estimation with unknown excitations (RLSE-UI). Structural damage at element level is detected by the degrading of stiffness of damaged structural elements. Numerical simulation of a 3-story building demonstrates the proposed method can identify structural element stiffness parameters with good accuracy and structural damage at element level can be located from the degrading of element stiffness parameters.