New method for FEM structural dynamic model updating and joint identification

A new structural dynamic model updating method is presented with focusing on identification of joint stiffnesses. It rests on a Reduced-Order Characteristic Polynomial (ROCP) defined in terms of joint stiffnesses, the measured natural frequencies and the modal properties determined from an initial FEM structural model. Based on the premise that each of the measured natural frequencies is a root of the RCOP, the unknown or suspicious joint stiffnesses are directly obtained from solving a set of nonlinear equations. Because the experimental data required in this method are simply the measured natural frequencies, one can effectively avoid many of the familiar difficulties associated with use of incomplete and less accurate experimental data such as modal vectors and frequency response functions. More importantly, the modal identities or orders of the measured natural frequencies are not necessarily known, that is, they are simply understood as some of the true natural frequencies for the structure. In practice, this implies that missing or mislabeling a mode is acceptable in a modal test. Therefore, the proposed technique has a potential for a substantial reduction of the resources spent on an experimental measurement and correlation analyses.