An advanced reduced model is proposed for elastic earthquake response analysis of shear building structures with setback. The proposed reduction method consists of two parts. The first stage is the construction of a reduced structural model with the degrees of freedom at representative floor levels only. The reduced model is constructed using an inverse eigenmode-problem formulation so as to have the same fundamental natural frequency and lowest-mode component ratios at the representative floor levels as the original model. The second stage is the transformation of earthquake input forces into a set of reduced input forces. This transformation is introduced to enhance the accuracy level of the reduced model.
