Invited Seminar by Dr. Nicholas Chan

Abstract: Modern buildings are designed to avoid collapse during earthquakes, but irreparable damage and residual deformation often make demolition more economical than repair. Passive dampers with self-centering capabilities offer a solution by concentrating all nonlinearity into dissipative joints, which also return structures to their original geometry. This raises a question: can such devices be adapted to systems traditionally prone to pinched hysteresis? If so, can they mitigate cyclic degradation and improve the feasibility of repairs after earthquakes? This question is explored through two systems that exhibit typical pinched behavior: timber shear walls and ordinary steel braced frames. Two dampers are presented, each achieving self-centering through a different mechanism. The pinching-free connector (PFC) employs a ratcheting mechanism to absorb slack from plastic deformation, while the Resilient Slip-Friction Joint (RSFJ) uses preloaded springs to provide restoring forces directly. The PFC is evaluated through quasi-static tests on a rocking timber wall and a steel braced frame, while the RSFJ is examined at building scale through shake-table tests on a three-story steel structure and a numerical study on device performance under sequential earthquakes. The results demonstrate that effective self-centering and damping are technically achievable across device types, structural systems, and loading scenarios, despite some system-specific behavioral phenomena with design implications. Yet, questions remain about the accessibility of such systems for wider adoption. This motivates ongoing research into a post-centering paradigm that optimizes damping and delays re-centering until after the earthquake subsides.

Biography: Nicholas Chan is a Marie Skłodowska-Curie Postdoctoral Fellow at TU Delft, where he is currently researching how vibrating friction dampers can enable buildings to recover their shape after earthquakes. His research spans the development, testing, and design of passive damper systems for earthquake-resilient steel and timber structures, drawing on experience from both research and industry. Before joining TU Delft, he spent three years as an R&D engineer at Tectonus, where he helped commercialize friction dampers across more than 30 projects internationally. He received his PhD from the University of Auckland and his bachelor's degree from the University of Canterbury. He is a recipient of the 2026 Young Researcher Award from the European Association for Earthquake Engineering.