A direct floor-response spectrum generation method for multiple degree-of-freedom structures

The seismic design of non-structural components (NSCs) has been extensively studied, particularly in the evaluation of floor response spectra (FRS) to enhance their performance during earthquake excitations. This paper aims to improve the current FRS evaluation methods by enabling direct generation of FRS without running time history analyses. For multiple degree-of-freedom (MDOF) supporting structures, modal FRS is calculated first based on the modal properties of both the MDOF structure and the NSC, and the input response spectra. A new combination method is proposed to combine the modal FRS that incorporates correlations between multiple modes. In addition, modified rigid response coefficients are introduced to enhance the accuracy of the estimated FRS. Furthermore, high frequency modes are included in a computationally efficient manner without the computational needs to evaluate the higher mode properties. The proposed method is examined on idealized multi-storey structures and a nuclear power plant auxiliary building for FRS evaluation. The results show that the proposed method captures the modal peaks and estimates FRS with consistently better accuracy compared with other FRS methods. • Correlation coefficients between FRS of multiple modes are derived analytically. • FRS-oriented rigid response coefficients are proposed for conservative results. • The high frequency modes are considered in a computationally efficient way. • The proposed method shows consistent accuracy in estimation of FRS.