Freddi, F; Dimopoulos, C; Karavasilis, T; (2019) Rocking Damage-Free Steel Column Base with Friction Devices: Design, Numerical and Experimental Evaluation. In: XVIII National Conference ANIDIS, L'Ingegneria sismica in Italia Proceedings. ANIDIS: Ascoli Piceno, Italy.

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Abstract

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 of 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 minimaldamage structures, which can reduce both repair costs and downtime. Examples of such structures include steel frames equipped with self-centering beam-column connections, structural fuses, passive energy dissipation devices, self-centering braces, and others. These earthquake-resilient steel frame typologies have been extensively studied during the last decade but little attention has been paid to the behavior of their column bases. Conventional steel column bases are susceptible to experience non-repairable damage significantly affecting the resilience of the entire structure. The present paper presents an innovative rocking damage-free self-centering steel column base and summarize the results of the analytical, numerical and experimental studies. The proposed column base uses posttensioned high strength steel bars and friction devices respectively to control the rocking behavior and to dissipate the seismic energy. The moment-rotation behaviors of the proposed column base can be easily described by using simple analytical equations allowing the definition of a design procedure for the calibration of the main design parameters with the aim of achieving the damage-free behavior, the self-centering capability and an adequate energy dissipation capacity. A three-dimensional non-linear finite element model of the column base was developed in ABAQUS in order to investigate the local behavior of the components, to validate the moment-rotation analytical equations and to demonstrate the efficiency of the design procedure. On the other hand, a simplified model for the column base was developed in OpenSees and allow to investigate the effects of the proposed column base on a case study building. Nonlinear dynamic analyses show that the rocking column base fully protects the first story columns from yielding and eliminate the 1 st story residual story drift without any detrimental effect on peak story drifts. In addition, an experimental campaign under monotonic and cyclic load protocols allows to calibrate the numerical models and further confirms the damage-free behavior and the high potentials of the proposed column base to be used in the design of highly resilient steel structures.

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