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Nominated for Eurosteel 2021 Best Paper Award In recent decades, innovative seismic‐resilient structural systems have been proposed to reduce the direct and indirect losses related to seismic events. Among others, steel moment‐resisting frames (MRFs) equipped with damage‐free self‐centring column bases (SC‐CBs) represent a promising solution. Although several configurations of SC‐CBs have been proposed in literature, only a few research studies investigated how the significant parameters (e. g. number of storeys, frame layout, seismic mass, seismic intensity) affect the seismic performance of MRFs with SC‐CBs. To further investigate this aspect, the present work focuses on the influence of an additional parameter (i. e. the combination of seismic mass and acceleration) on their self‐centring capability. Three 5‐bay steel MRFs with 4, 6 and 8 storeys are considered as case‐study frames and designed based on two different values of the seismic mass (i. e. M1 and M2). Numerical models are developed in OpenSees, incremental dynamic analyses (IDAs) are performed to monitor global engineering demand parameters (EDPs), and fragility curves are derived to evaluate the seismic performance of the structures. It is observed that the inclusion of SC‐CBs produces beneficial effects in terms of increased self‐centring capability on all the investigated case studies. Moreover, the parametric analysis allows some preliminary observations to be drawn regarding the influence of the number of stories and seismic mass.

In the last two decades many researchers focused on the development of innovative building structures with the aim of achieving seismic resilience. Among others, steel Moment Resisting Frames (MRFs) equipped with friction devices in beam‐to‐column joints have emerged as an effective solution able to dissipate the seismic input energy while also ensuring the damage‐free behaviour of the system. However, to date, little attention has been paid to their column bases, which represent fundamental components in order to achieve resilience. In fact, column bases designed by current conventional approaches lead to significant seismic damage and residual drifts leading to difficult‐to‐repair structures. The present paper evaluates the seismic performance of steel MRFs equipped with an innovative damage‐free, self‐centring, rocking column base joints. The proposed column base consists of a rocking splice joint where the seismic behaviour is controlled by a combination of friction devices, providing energy dissipation capacity, and pre‐loaded threaded bars with disk springs, introducing restoring forces in the joint. The design procedure of the column base is presented, a numerical OpenSees model is developed to simulate the seismic response of a perimeter seismic‐resistant frame, including the hysteretic behaviour of the connection. Non‐linear dynamic analyses have been carried out on a set of ground motions records to investigate the effectiveness of the column base in protecting the first storey columns from yielding and in reducing the residual storey drifts. Incremental Dynamic Analyses are used to investigate the influence of the record‐to‐record variability and to derive fragility curves for the whole structure and for several local engineering demand parameters of the frame and of the column base connection. The results show that the damage‐free behaviour of the column bases is a key requirement when self‐centering of MRFs is a design objective.

In recent years there have been significant advancements in the definition of innovative minimal damage structures chasing the urgent requirements of more resilient societies against extreme seismic events. In this context, a type of seismic‐resilient moment resisting frames (MRFs) is based on the use of Self‐Centring Damage‐Free (SCDF) devices in column bases and beam‐to‐column joints. However, when these devices are widespread across the whole structure, the details' complexity increases significantly with respect to conventional solutions, thus limiting their practical application. To overcome this drawback, current research works are focusing on the definition of optimum locations for SCDF devices such that their effectiveness is maximised. Within this context, the present study investigates optimum locations for a limited number of SCDF devices to be used within mid‐ and high‐rise MRFs. An 8‐storey structure is selected for case study purposes and nineteen configurations are investigated considering different positions of SCDF joints. Numerical models of the selected configurations are developed in OpenSees and Incremental Dynamic Analysis are performed. The seismic responses of the case‐study structures equipped with different layouts of SCDF devices are evaluated and compared. Some considerations in terms of optimal distributions of SCDF devices are made with the aim of maximising the efficiency of the solution and the seismic performance of mid‐ and high‐rise MRFs.

In the last two decades, increasing efforts have been devoted to the definition of innovative seismic design philosophies, with the aim of reducing seismic induced direct and indirect losses. Among others, beam-to-column connections equipped with friction devices have emerged as an effective solution to dissipate the seismic input energy while also enhancing the damage-free behaviour of steel Moment Resisting Frames (MRFs). Additionally, recent numerical studies have demonstrated the benefits deriving from the replacement of conventional full-strength column bases (CBs) with innovative damage-free and self-centring CBs, for both damage and residual drifts reductions of low-rise MRFs. Within this framework, an experimental campaign has been planned on a two-storey one-bay large-scale case-study MRF equipped with damage-free self-centring CBs. The present paper illustrates the preparatory work required for the design of the specimen, the test setup, and the Pseudo-Dynamic test procedures, and aims at foreseeing the response that will be observed during the experimental test by advanced numerical simulations in OpenSees. Non-linear time history analyses have been performed considering ground motion records scaled to several intensity levels. The preliminary numerical results provide useful information for the selection of the accelerograms to be used during the tests and on the expected response of the structure.

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