Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A theoretical study of the soil-structure interaction effects on the dynamic behaviour of structures is presented. The substructure approach is employed for which foundation impedance functions are derived from static and dynamic continuum theories. Both rigid and flexible structures supported by various types of foundations are investigated. The free vibration analysis of the soil-structure interaction system indicates that the damped natural frequencies of structures on flexible foundation may be lower or higher than the undamped natural frequencies. It also shows that the foundation flexibility provides damping to the structure due to energy dissipation in soil and modifies the original structural damping. The effect of the foundation on the damping of structures is calculated using an energy consideration and by means of the complex eigenvalue analysis. Both methods give almost the same results for the first mode but may give considerably different results for the higher vibration modes.;The dynamic response of the soil-structure interaction system excited by shock, earthquake and wind loading is investigated. The analysis of hammer foundations, the most typical of the shock experiencing structures, proves that the complex eigenvalue method is an efficient and accurate method of response prediction. Using this approach, the response of hammer foundations to either initial velocity of the anvil or pulse loading can be treated for any number of degrees of freedom.;Seismic loading and response of buildings depend on the flexibility of the foundation and its type. Shallow flexible foundations may increase the response and decrease the seismic forces of the structure, as compared to the response of the same structure on a rigid base. For pile foundations, the number and type of piles, their arrangement and the pile connection with the cap come into play. The study shows that, for small buildings and/or low intensity of earthquakes, the rigid connection of piles with the cap may not be necessary. The response of rigid structures to seismic loading is dealt with efficiently using the direct random vibration analysis.;Finally, the effect of foundation flexibility on structural response to gusting wind is explored using the gust factor approach. The parametric study indicates that while the gust effect factor may or may not be sensitive to soil flexibility, the resultant vibration may be substantially modified.



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