Repairable Steel Moment‐Resisting Frames for enhanced Seismic Resilience: conceptual and numerical investigation

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Abstract In recent years, the increasing demand for seismic‐resilient structures has progressively redefined the seismic design performance objectives. Structural design is no longer limited to ensuring life safety, but is increasingly oriented toward enabling the rapid restoration of both structural integrity and operational functionality, even after severe earthquakes. Within this evolving context, structural repairability is emerging as a key performance objective, allowing damage to be mitigated through simple and efficient repair strategies with limited or no component replacement. In line with these objectives, the R4STEEL project focuses on the development of resilient and repairable steel Moment Resisting Frames (MRFs) equipped with innovative self‐realigning connections. This paper presents a numerical investigation aimed at evaluating and comparing the seismic performance and repairability of two MRF typologies: a conventional MRF, and a repairable MRF combining friction and self‐centring column bases (Re‐MRF). Two different building heights (4‐storey and 8‐storey structures) are considered, resulting in a total of four case‐study configurations. Incremental Dynamic Analyses (IDA) are performed in OpenSees to assess the seismic response of the examined systems. An innovative post‐earthquake repair strategy based on the controlled loosening of bolts in the friction joints is numerically investigated. The results show that the 4‐storey Re‐MRF exhibit an inherently self‐realigning behaviour, whereas in the 8‐storey configuration the self‐realignment capability is reduced. However, the residual drifts are significantly mitigated through controlled bolt loosening along the elevation.

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