In order to investigate the dynamic properties of castellated beams, the excitation intensity of
dynamic mode shapes for different loading patterns must be considered. Obviously, under a specific
loading pattern, all of dynamic mode shapes are not excited. In other words, the response of the structure is
dependent on the exerted loading. In this article, the powerful FEM software, ANSYS is used for
investigation of dynamic properties of castellated beams. At first, a modal analysis is performed on both
plain-webbed and castellated cantilever beams with two different types of lateral bracing and their dynamic
properties and mode shapes are studied. This analysis shows that the presence of large web openings may
have a severe penalty on the load carrying capacities of castellated beams under the dynamic gravitational
loads. Then a white noise dynamic load with an appropriate frequency range is exerted on both plainwebbed
and castellated beams and their various dynamic responses are studied. It can be seen that the
loading pattern is a very important factor for investigation of dynamic properties of cantilever castellated
beams.