System Test of a Base-Isolated Building

Shake table testing of a base-isolated building was conducted at the NEES facility at University of Nevada, Reno. A 1/4 scale 3-story steel frame building with lead-rubber bearings was subjected to a variety of motions. The system response was recorded using the following instruments: load cells to record the bearing forces, string pots to record the bearing displacements and superstructure story drifts, and accelerometers to record the superstructure floor accelerations.

The test program incorporated single and bi-directional sine waves and earthquakes of different intensities. For this experiment, all motions were scaled in a way to target an isolator displacement of 5.7 inches at the maximum intensity. Each sine wave or earthquake motion was applied in a ramp-up sequence of increasing intensities building up to the maximum target.

This experiment was designed as a reference to evaluate the performance of the gap damper in Experiment 3. To the extent possible, identical input motions were applied to the system in Experiments 2 and 3. Furthermore, some of the trials were repeated at the end of Experiment 2 to document the consistency of the isolation system response over the course of the experimental program.