A new dynamic reanalysis method for large structure modification

Dynamic Analysis involves the determination of natural frequencies and modal shapes. It can be an expensive process for a larger model. During a design optimization process, analysis is conducted at each iteration. If a complete analysis is performed repeatedly for each design iteration, the cost would be formidable. A number of approaches for dynamic reanalysis have been published in the past years to reduce the CPU time for dynamic reanalysis. However, most of those methods are good only for small design modifications. This paper presents a new dynamic reanalysis method. The proposed method is based on a differential equation which is derived from the governing equation of motion for dynamic systems. The design parameters are the independent variables. The natural frequencies and modal shapes are the dependent variables. The natural frequencies and modal shapes of initial design are the initial values of the dependent variables. By solving this differential equation, the natural frequencies and modal shapes of the modified structure are obtained. The computational time used for this solution is significantly reduced compared to a complete dynamic reanalysis.