Prediction of the response of secondary structures under dynamic loading considering primary-secondary structure interaction

In current seismic design, earthquake-induced forces in secondary structures are estimated from the acceleration of the primary structure at the support of the secondary structure. However, recent studies had shown that the response of the secondary structure can significantly affect that of the primary structure, which will simultaneously modifies that of the secondary structure. To accurately estimate the response of the secondary structure, the interaction at the interface of the two structures needs to be considered. In this study, a scaled model consisting of primary and secondary structures was designed to capture the interacting forces. The degree of fixity of the secondary structure was varied. Two types of dynamic loading, that is, impact and harmonic loads, were applied to the model structures. The relationship between the interacting force and the response of the secondary structure is discussed. Empirical formulae for predicting the maximum displacement of the secondary structure based on the displacement spectrum at its base were proposed. The formulae provided more accurate prediction of the top displacement of the secondary structure considered, in comparison with that obtained from a conventional floor response spectrum.