Design, Numerical Simulation, and Experimental Evaluation of a Rocking Damage-Free Steel Column Base with Friction Devices

Conventional seismic-resistant structures, such as steel moment resisting frames, are designed to experience significant inelastic deformations under strong earthquakes. Inelastic deformations result in damage in structural members and residual interstory drifts, which lead to high repair costs and disruption of the building use or occupation. The aforementioned socio-economic risks highlight the need for widespread implementation of minimal-damage structures, which can reduce both repair costs and downtime. Examples of such structures include steel frames equipped with post-tensioned beam-column connections, passive energy dissipation devices, self-centering braces, and other smart structural details. These earthquake-resilient steel frame typologies have been extensively studied during the last decade but little attention has been paid to the behaviour of their column bases. The paper presents an experimental program on a damage-free rocking steel column base which uses posttensioned high-strength steel bars to control rocking behaviour and friction devices to dissipate seismic energy. Contrary to conventional steel column bases, the proposed rocking column base exhibits monotonic and cyclic moment–rotation behaviours that are easily described using simple analytical equations. The latter allow the development of a practical step-by-step design procedure, which ensures damage-free behaviour, self-centering capability, and adequate energy dissipation capacity for a predefined target column base rotation. The experimental behaviour of the column base under monotonic and cyclic loading protocols confirm its selfcentering and damage-free behaviour even under very large rotations