Experimental study of bi-directional spring unit in isolated floor systems

In the US, isolated floor systems are gaining interest in various applications to protect nonstructural components that can be moved and located anywhere on the floor or specific rooms - instead of isolating single equipment or the entire building. To investigate the mechanical behavior of bi-directional spring units used as isolators in a kind of such isolated floor systems, three types of characterization tests were conducted - from spring components alone to the complete spring unit in its implemented configuration. The test results show that the behavior of the springs and spring units is stable when subjected to cyclic repeated motions, and is not sensitive to the velocity of motion. The hysteretic behavior of the spring units was found to be unconventional, with bilinear and different ascending (loading) and descending (unloading) branches. All these results provide the foundation to develop a physical model for engineers to better understand the behavior of such kind of bi-directional spring units and the corresponding isolated floor system.