Innovative seismic isolation strategies for equipment and non-structural components: Experimental investigation and analytical modeling of systems isolated with spring-viscoelastic mounts

Seismic events pose major challenges to the integrity and safety of critical infrastructure. Ensuring the uninterrupted functionality of lifeline facilities, such as hospitals, data centers, and industrial plants, requires safeguarding essential systems during and after earthquakes. In this context, the protection of nonstructural components, including HVAC equipment, generators, and UPS systems, is fundamental to operational continuity. As shown by Taghavi and Miranda [2003], non-structural damage can dominate earthquake-induced economic losses, reaching 82% in office buildings, 87% in hotels, and 92% in hospitals. Reducing these vulnerabilities is therefore central to both resilience and service continuity. In the previous study, Awad et al. [2024] investigated the seismic performance of an industrial chiller equipped with spring anti-vibration mounts through triaxial shaking table tests. Displacement, acceleration, and frequency response were measured in accordance with established seismic qualification standards, namely ICC-ES AC156 [2010], IEEE Std 693 [2018], and IEC 60068-3-3 [2019], and complementary analytical models were developed to reproduce the behavior of vibration-isolated equipment with flexible connections. Building on this evidence, a novel seismic isolation system is proposed, combining induced tilting mechanisms with viscoelastic fluid dampers. Spring-viscoelastic anti-vibration mounts, traditionally applied to heavy machinery, are adapted here for lighter equipment (<10 tons). Unlike ball bearings or PTFE sliders, the system provides vertical restraint while preserving isolation efficiency under high deflections. The use of polyisobutylene fluid ensures effective low-frequency damping, thereby improving vibration control and reducing seismic demands.