Identification of system parameters and input force from output only

A method based on sensitivity of structural responses is presented for identifying both the system parameters and the input excitation force of a structure. Both sinusoidal and impulsive forces are studied. In the inverse analysis, a short length of measurement from only one or two accelerometers is required, and an iterative gradient-based model updating method based on the dynamic response sensitivity is adopted. The location of the input force is assumed known in the identification. The poor identification with the relatively insensitive parameters in a mixture of parameters with different sensitivities is addressed and solved with another loop of optimization. Validity of the proposed method is demonstrated with two numerical simulations and verified with laboratory results from a simply supported steel beam.