ELEMENT-LEVEL SYSTEM-IDENTIFICATION WITH UNKNOWN INPUT

A finite element-based time domain system identification procedure is proposed to evaluate existing large structural systems at the element level. The procedure does not need any information on the input excita tion forces. Since the input exciting forces are not required, there i s no restriction on the type of exciting force, only a small number of observation time points are required and no information is required o n the modal properties of the structure. The unknown exciting forces c an be applied at the ground level representing the seismic excitation. The procedure is particularly applicable to identifying an existing s tructure. The method is verified using three examples. For verificatio n purposes, both the noise-free and noise-included output responses ar e considered. In all cases, the proposed method identified the structu ral parameters very well. The errors in the estimation of the paramete rs are considerably smaller than those in the other methods currently available in the literature. The proposed method is very economical, s imple, and robust.