termining the dynamic properties of castellated beams using the white-noise

in investigation of dynamic specifications of castellated beams, it is necessary to be studied the excitation intensity of dynamic mode shapes for different loading conditions. it is evident that for a specific loading, not all modes of a structure are excited and the structural response depends on the applied loading specifications. in this paper using the finite element method (based on ansys software), a dynamic load with properties of white noise in a proper frequency range is applied on the both cantilever catellated and plain webbed beams. the dynamic specifications and different excited modes of them are taken into investigation. it could be seen that the loading conditions are very important in order to excite and define the dynamic specifications of these beams. in a uniformly loaded cantilever beam with the white-noise properties, merely some of the vibration modes, that is, the flexural modes are excited and the effects of some of the other modes such as torsional modes are eliminated. therefore, in order to excite all of the vibration modes a loading with proper frequency band should be applied. also it should be mentioned that the current method indicates that castellated beams are weak in comparison with plain webbed beams subjected to dynamic gravity loads which cause bending moments and excite the flexural modes.