Rotational components in structural loading

• The rotational loading of multistory buildings is studied.
• Simple methods for estimation of earthquake rotational components and their SDFs are proposed.
• A practical method to include effects of kinematic interaction in evaluating FIMs is presented.
• Torsional and translational response spectra with considering foundation effects are compared.

In this paper, the rotational loading pattern of multi-storey buildings supported on the spread and continuous interconnected single foundations is discussed. To achieve this, simplified relations for the estimation of (1) point rotations; (2) spatial variation of strong ground motions, and (3) foundation input motions are derived. The height-wise variation of the earthquake rotational loading of multi-storey buildings is parametrically evaluated by considering the location of the first rigid floor diaphragm and foundation type. In addition, the effect of the kinematic soil–structure interaction on the response spectrum of the rotational and translational components is studied. The numerical results provide a deeper insight into the rotational loading of structures in the middle-field zone, and show how the rotational components may detrimentally affect the structural response of multi-storey buildings depending on their kinematic characteristics.