Development of New Self-centring Rocking Systems by Incorporating Resilient Slip Friction Mechanisms: Applications in Structures and Storage Tanks

Abstract

Rocking systems, encompassing walls, columns and frames, have emerged as effective structural configurations in mitigating seismic hazards by providing the desirable displacement ductility, demonstrated by their robust bilinear elastic response. Initially conceptualized for gravity load applications, their resilience across various natural disasters (including hurricanes, tornadoes, and earthquakes) has substantiated their competence as primary lateral load-resisting structures. In recent decades, this conventional concept has been augmented by incorporation of energy dissipation mechanisms and hold-down systems to enhance the structure hysteresis performance by reducing the amplitude of oscillation during an event. This has fostered a low-damage, stable, and reliable seismic performance. The fundamental efficacy of rocking systems is attributed to the rotational freedom provided to structures, facilitating the synchronicity with seismic motions and consequently mitigating the impact of seismic forces on structural components and their connections. To ensure the stability of such systems, integration with stabilizing mechanisms is imperative. Moreover, the inclusion of additional damping mechanisms is critical for maintaining deflections within permissible limits. The utilization of self-centring friction dampers, which includes both restoring and energy damping features, is particularly advantageous for rocking system applications. This research focused on the seismic performance of two distinct applications of rocking systems equipped with self-centring friction dampers: cylindrical steel liquid storage tanks and rocking panel walls. The initial phase of this study investigated the rocking behaviour of conventionally designed cylindrical steel tanks, equipped with an innovative hold-down system to reduce the earthquake load demand and enhance their seismic resilience. This phase was commenced with the experimental component testing to validate the performance of a specially designed self-centring friction damper suitable for this application. Subsequently, a comparative seismic performance analysis was conducted on several case studies of cylindrical steel storage tanks, comparing the effects of the proposed anchorage system with the current state-of-practice such as necked rods and buckling-restrained hold-downs. The second phase of the study proposed a novel rocking panel by integration of self-centring dampers, functioning as shear keys on both sides of the panel (rather than hold-downs). The objective was to introduce a new damage-free rocking system as a primary lateral resisting mechanism, applicable to both new structures and retrofitting of existing earthquake-prone building. Initially, the effectiveness of this system was validated through numerical modelling, followed by the design and testing of a large-scale rocking concrete panel incorporating the proposed configuration.