Structural Dynamics Modification (SDM) is widely used to change natural frequencies and/or mode shapes by adding and deleting auxiliary members for improving the dynamic response of a target structure. Most of the existing SDM approaches deal with the material property or the size of structures for a given structural layout having matched nodes. In this work, an attempt is made to place the modification structural elements on the baseline structure by determining their translational positions and the rotational orientations, thus effectively realizing the redesign of the layout of modifying structures in spite of non-mating nodes between substructures for improving the natural frequencies of the resulting structure.
The interface frame concept is adopted for an effective layout optimazation and non-matching node problem. The interfacing displacements of modifying substructures are constrained to those of the baseline structure during optimization process. Thus remeshing process is not needed.
Since the attaching structure moves continuously on the baseline structure, sensitivities to determine the moving direction are essential for each optimization iteration. The eigenvalue and eigenvalue sensitivities of the attaching structure to the moving direction of the attaching members are formulated using the Simpson method. This technique is also applied to optimal supporting problem.
Finally, the optimal structural modification is obtained by iteratively carrying out the eigenvalue sensitivities and eigenvalue reanalysis. Numerical examples demonstrate the effectiveness of the proposed SDM approach.
구조물 동특성 변경법(SDM)은 변경 구조물의 첨삭을 통해서 기저 구조물의 고유치나 고유 형상을 변경하는 방법이다. 기존의 동특성 변경법은 기저 구조물과 변경 구조물 사이에 절점이 일치된 상태에서 수행되었으며, 변경 구조물의 크기나 물성치를 디자인 변수로 사용하였다. 본 연구에서는 불일치 절점이 있는 경우에도 적용 가능한 구조물 동특성 변경법을 다루었다. 구조물의 동특성을 변경하기 위한 디자인 변수로는 결합 위치를 고려하였으며, 절점을 일치시키기 위한 요소망 재생성이라는 번거로운 과정이 필요 없는 구조물 동특성 변경법을 제안한다. 또한 효과적인 동특성 변경을 위해 결합 위치에 대한 고유치의 민감도 식을 구성하여 구조물 최적화에 적용하였다
