THE EFFECTS OF ROTATIONAL INERTIA ON THE RESPONSE OF DYNAMICALLY LOADED STRUCTURES

ABSTRACT

Engineering structures subjected to dynamic loading exhibit vibration motions. These vibrations induce accelerations on the structures and their component parts. The accelerations in turn generate inertia forces that propagate the vibrations and significantly affect the response of the structures and their components parts to external loading. This cyclic cause and effect situation result in randomly oriented and time-dependent displacements as the basic response criteria of structures that are subjected to dynamic perturbations. Researches have shown that translational and rotational inertia are exhibited in the cause of these vibrations. Consequently, it was concluded that translational and rotational inertia are generated in structures under dynamic loading. However, translational inertia has, over time, been the subject of research in dynamic analysis of engineering structures. It is often the only inertia force considered in analysis, design and determination of the important response criteria of structures operating in dynamic environments. Indeed the effects of all significant inertia forces should be considered in the analysis and design of dynamically loaded structures. This is to ensure that the results to be obtained will truly simulate real conditions.  This work seeks to investigate the effects of rotational inertia on the response criteria of structures subjected to dynamic perturbations. The results obtained from the numerical solutions of the equations of motion developed show that some important fundamental natural frequencies are obtained with the consideration of rotational inertia. The solution of the equations of motion also show that there are significant increases in the internal stress distributions evaluated when rotational inertia is taken into consideration.  It is evident; therefore, that rotational inertia can no longer be ignored in the analysis of dynamically loaded structures because the internal stress distributions and other response criteria are significantly affected by rotational inertia forces.