Dynamic Analysis of Skeletal Frames Subjected to Ground Motions: A Theoretical and Experimental Study

In this study it was intended to study both the mathematical and experimental behaviour of skeletal frames and to examine the feasibility of using small scale models to predict the behaviour of prototype structures. Mathematical analysis of both two and three dimensional structures was carried out. Computer programs were written using the relevant mathematical models and response of typical structures subjected to ground motions. For two dimensional frames both linear and nonlinear behaviour of structures was studied. For three dimensional structures to reduce the size of the eigenvalue problem, a technique known as Dynamic Condensation was incorporated. To carry out the experimental study on small scale models, a small unidirectional shaking table was designed and constructed in the departmental workshop. Two small scale models were tested using this table. The natural frequencies for these models were obtained experimentally and their response to both harmonic and random vibrations was studied. Comparisons were made between the experimental values recorded and theoretical values obtained by using the computer programs. The correspondence between experimental and analytical results was reasonably good for both the models. Experimental losses and distortions produced during fabrication procedures lead to experimental values being smaller than the corresponding theoretically computed values. It was not possible to induce nonlinear behaviour in either of the models due to the limited capabilities of the experimental equipment used. From this study it can be concluded that the use of small scale models can be successfully used to predict the dynamic behaviour of simple prototype structures. It is however essential to accurately design and construct these models to represent the characteristics of the prototype being studied