Effect of pounding on the seismic response of two adjacent asymmetric buildings under single uni-directional ground motion

The aim of this paper is to present a detailed analytical study able to simulate the earthquake induced lateral-torsional pounding between two multi-storey adjacent buildings with different dynamic properties. Coupled lateral-torsional pounding between asymmetric structures has been investigated only in the last decades, but always with reference to impact between two single-storey structures, while most of the existing buildings are of course multi-storey. Moreover in many cases contact is modelled by linear impact elements, while contrarily pounding models utilizing the non-linear Hertz contact law appear to be more realistic, earthquake poundings being highly non-linear phenomena. For this reason in the proposed model both a non-linear viscoelastic model to simulate impact and a non-linear behaviour of the storey shear forces and torques are considered, differently from many commercial codes which admit just one non-linearity. Torsional effects are taken into account by implementing all the possible impact scenarios, depending on the sign of the rotations of two adjacent floor-diaphragms. Moreover it is assumed that, at each storey-level, pounding occurs when a corner of one building impacts onto an arbitrary point of the other building. Just single uni-directional earthquake ground motion is incorporated in the analysis. As a consequence pounding-induced response is evaluated exclusively in the seismic direction, also due to the small values of rotations involved in the analysis. The results show the significance of coupled lateral-torsional pounding responses on adjacent structures. Torsional vibrations of both structures are important components of the overall structural response and mainly influence the number of impacts.