In the seismic design of secondary systems (SS) such as nonstructural components, the effect of torsional vibrations of structural frames due to asymmetric properties are not explicitly considered. The effect has been investigated for relatively small SS, but not for large ones. In this paper, seismic response of symmetric large SS installed in continuous broad areas in single-story asymmetric buildings are investigated through response history modal analysis. The torsional response of symmetric SS and the correlations between modal responses are discussed. From the results, peak responses of large SS are shown to be almost equal to those of corresponding small SS.
