Structures designed in accordance with even the most modern buildings codes are expected to sustain damage during a severe earthquake; however; these structures are expected to protect the lives of the occupants. Damage to the structure can require expensive repairs; significant business downtime; and in some cases building demolition. If damage occurs to many structures within a city or region; the regional and national economy may be severely disrupted. To address these shortcomings with current seismic lateral force resisting systems and to work towards more resilient; sustainable cities; a new class of seismic lateral force resisting systems that sustains little or no damage under severe earthquakes has been developed. These new seismic lateral force resisting systems reduce or prevent structural damage to nonreplaceable structural elements by softening the structural response elastically through gap opening mechanisms. To dissipate seismic energy; friction elements or replaceable yielding energy dissipation elements are also included. Post-tensioning is often used as a part of these systems to return the structure to a plumb; upright position (self-center) after the earthquake has passed. This paper summarizes the state-of-the art for self-centering seismic lateral force resisting systems and outlines current research challenges for these systems.

Mass timber is an attractive and sustainable alternative structural engineering material to concrete and steel. Despite successful midrise to high-rise timber building projects around the world, such buildings have not been implemented in regions with high seismicity due in part to a lack of research and development on appropriate ductile seismic load resisting systems for heavy timber construction. This paper describes experiments conducted to develop a resilient lateral force-resisting wall system that combines cross-laminated timber (CLT) panels with vertical posttensioning (PT) to provide postevent recentering. Supplemental mild steel U-shaped flexural plate (UFPs) are intended to yield under cyclic loading while the PT and CLT components remain undamaged until large interstory drifts are experienced by the wall. The experiments were designed to explore various limit states for self-centering CLT (SC-CLT) walls, including their dependence on design variables and their effect on performance, and to investigate strength and stiffness degradation at large interstory drifts. It was found that the SC-CLT walls were able to recenter even after large drift cycles and the crushing of the CLT material was the governing limit state for most specimens. A hierarchy of desirable limit states was identified consisting of UFP yielding, CLT splitting, PT yielding, and CLT crushing.