Base shear capping buildings with graphite-lubricated bases for collapse prevention in extreme earthquakes

Damage or collapse of buildings vulnerable to seismic forces may cause human casualties, and seismic upgrading of such structures is a practical solution to this deficiency. The study presented here proposes a simple approach to prevent structural collapse by separating the superstructure from its foundation to let the superstructure slide during extreme ground shaking. The sliding mechanism contributes to cap the horizontal force exerted on the superstructure. In such approach, the key is to maintain the friction force between the superstructure and the foundation sufficiently low and stable. This research proposes to realize a controlled sliding mechanism, which acts as a structural fuse, by means of carbon powder lubrication at the bases of the structure's columns. The fundamental behaviour of the proposed structural system, named the base shear capping building, is investigated by shaking table tests and numerical simulation. Both experimental and numerical results showed that graphite lubrication is an efficient and robust lubrication material, maintaining the friction coefficient between the steel column bases and mortar foundation at around 0.16. The sliding at the bases significantly reduced the acceleration transmitted to the superstructure, keeping the base shear coefficient not greater than about 0.40. Copyright © 2016 John Wiley & Sons, Ltd.