ENABLING STRUCTURAL MODIFICATION THEORY FOR OMA

OMA has many practical advantages and has been established in the recent years. The disadvantage of unscaled mode shapes remained. Papers in the past have shown, that measurements with and without additional mass make it possible to find the scaling factor modal mass. The amount of additional mass can be optimized on the error estimations of the OMA data. Based on that classical FRFs can be synthesized and this paper show how structural modifications can be analysed on this FRF basis. Simple applications are mass, damping or stiffness modifications at single DOF. A more elaborate application is the structural coupling. Here also rotational DOF have to be considered. Other requirements are correct rigid body modes and no modal truncation. The theory is explained in detail and examples are shown for physical data.