Effects of distributed structural dynamic modification with additional degrees of freedom on 3D structure

The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic response of a complex structure. Although structural modification has been demonstrated as an efficient method for both 1D structure with distributed modification with/without additional degrees of freedom (DOFs) and 2D structure with distributed modification with reduced DOFs, research into structural modification of 3D structures with additional DOFs has been limited. In this paper, structural modification has been applied to a 3D box frame clamped on one edge or with free–free boundary condition with a plate attached on another side as modification. The frequency response functions (FRFs) of the original unmodified 3D frame were obtained experimentally as well as numerically. The delta dynamic stiffness matrix was determined numerically by modeling the attachment and part of the original structure. The FRFs of the modified 3D frame are computed by coupling the original FRFs and the delta dynamic stiffness matrix. Good agreement is obtained between the FRFs of the modified 3D frame determined experimentally and those obtained by numerical modeling of the complete modified structure. Structural modification method has been verified on 3D structure for distributed modifications with additional DOFs, and also it has been verified on coupling two different types of structures, beam and plate.