ABSTRACT

The dynamic analysis of discontinuous structures has gained the attention of researchers over past decades because of their ability to resist dynamic loading such as wind, waves, earthquakes, traffic, blasts and explosion, as well as the increasing demand for better performance, assisting in weight reduction and easy assembling of structure.  Due to reduction in computational time and cost, advancement in numerical methods and the availability of powerful computing facilities, analytical models have become the most popular technique for dynamic analysis of such structure.  In this study, an improved analytical model that uses receptance model based on Timoshenko beam model for the dynamic of discontinuous beam in order to obtain the modal parameter was proposed.  The Timoshenko beam model was modified based on transverse response of beam at first three modes in order to overcome its shortcomings. To clarify the implementation of the proposed model, two types of discontinuities, namely, stepped beam with aligned and misaligned neutral axes, were considered and numerical simulations provided to demonstrate the modal parameter and frequency response of the structure. Additionally, a flexible multi-configuration beam vibration testing rig was modified and experimental modal analysis (EMA) of uniform and discontinuous beams provided.  Results obtained were compared to other analytical techniques and experiments. The results of the proposed analytical model showed identical result with experiment with at most 0.99% deviation from the experimental results for all frequency modes.  The result when compared with other analytical technique shows at most 92% frequency deviation with reference to the proposed analytical model for all frequency modes.  It was also found that increase in the discontinuity depth and discontinuity location for the natural frequencies produced irregular curves for free-free boundary configurations.  Application of the modified model to other designed model analysis as observed, produced a good correlation between experimental and analytical results.  The proposed model can also be extended easily to deal with various discontinuous structures as well as a helpful tool in different structural analysis, thereby increasing the quality of the product, safety, reliability and performance of structures.