Post-earthquake functionality assessment of MRFs enhanced by resiliently lateral-resistant and bottom systems

The accumulated stiffness and strength degeneration of rigid bottom joints and uneven lateral deformation mode of the moment-resisting frame (MRF) during earthquakes can result in disastrous structural failures. Damage accumulation, excessive residual inter-story drift, and the lack of self-centering behavior and energy-dissipation capacity in structures are major challenges in controlling losses after earthquakes. This paper aims to propose a self-centering energy-dissipation (SCED) system that enhances the seismic performance of MRFs. This system, called the resilience-enhanced MRF (ReMRF), utilizes a rocking truss as a lateral-resistant structure and incorporates two bottom joints with SCED capabilities into the MRF design. These bottom joints, referred to as the Buckling Restraint Steel Plate (BRSP) bottom joint and the Light Self-Centering (LSC) bottom joint, are composed of key components such as BRSPs and post-tensioned (PT) strands, respectively. Structural design methods and parameters for the rocking truss and bottom joints are discussed to determine optimal values for balancing stiffness demand, SCED capacity, and construction convenience. Special attention is paid to the working stability of the bottom joints during earthquakes and the effectiveness of the SCED system. Results indicate that the performance of the bottom joints and the SCED system is in line with expectations. The findings from both pushover and time history analyses have substantiated that ReMRF outperforms MRF in terms of achieving higher seismic performance objectives. It is intuitively demonstrated by several quantitative metrics derived from static and dynamic analyses, including the overstrength factor, ductility factor, drift concentration factor, peak inter-story drift, and residual inter-story drift.