In many countries, seismic isolation technology is increasingly being used to improve the performance of buildings and bridges and avoid significant structural damage by concentrating large deformations in the isolators and providing supplemental energy dissipation through the isolation system during ground shaking. For various reasons, the isolation plane is no longer always placed at the base of the building as was common practice historically. Over the last decade, midlevel seismic isolation systems, where the isolation plane is placed higher up the building instead of at the base, have been studied [1, 2, 3, 4] and several tall midlevel isolation building projects have been designed and constructed, especially in Japan [5, 6]. Midlevel seismic isolation systems can provide the following benefits versus conventional tall building construction practices:
• Provide more architectural flexibility, necessary in multi-use applications where transitions between different structural systems are required.
• Concentrate deformations and energy dissipation in the isolation level, reducing seismic demands on both the super- and substructure and eliminating structural damage.
• Facilitate the addition of new stories on top of existing buildings while minimally increasing seismic demands on the existing building by exploiting the unturned mass-damper effect that is introduced by the isolated superstructure.
However, because the dynamics of midlevel isolated buildings is dependent on the interaction between the sub- and superstructure, multiple large scale configurations become unfeasible by standard experimental testing methods. In order to efficiently test the interaction between an isolated superstructure with a range of substructure configurations, the hybrid shake table testing method was adopted [7]. Friction pendulum bearings were selected for the isolation bearings, which exhibit a strong rate-dependency especially at low velocities; thus, the hybrid control needed to be in real time and a unidirectional hybrid shake table was built for the project. This setup allows for extended study into the behavior of midlevel isolated buildings.