AbstractA procedure is described to compute the lateral and rotational floor response spectra of an asymmetric reactor building structure without a time history analysis. The spectral values obtained by filtering the prescribed ground motion first through the structure and the resulting lateral‐rotational motions through simple oscillators are equal to the maximum lateral‐rotational responses of the structure developed when the order of filtration is reversed. Based on the preceding concept a deterministic method is presented to construct the lateral‐rotational floor response spectra utilizing the response spectrum tech