Identification and tracking of structural parameters with unknown excitations

System identification and damage detection for structural health monitoring of civil infrastructures have received considerable attention recently. The traditional least square estimation (LSE) method requires that the external excitation data (input data) be available, which may not be the case for many structures. A recursive least square estimation with unknown inputs (RLSE-UI) approach is proposed to identify the structural parameters, such as the stiffness, damping and other nonlinear parameters. Analytical recursive solutions for the proposed RLSE-UI are derived and presented. An adaptive tracking technique recently developed is also implemented in the RLSE-UI approach to track the variations of structural parameters due to damages. Simulation results using an ASCE benchmark building for structural health monitoring demonstrate that the proposed RLSE-UI approach is capable of identifying the structural parameters and their variations due to damages.