System Test of a Base-Isolated Building with Gap Damper

Shake table testing of a base-isolated building with a gap damper device was conducted at the NEES facility at University of Nevada, Reno. A 1/4 scale 3-story steel frame building with lead-rubber bearings and a gap damper device installed beneath the base of the building was subjected to a variety of motions. The system response was recorded using the following instruments: load cells to record the bearing forces and damper forces; string pots to record the bearing displacements, damper stroke, 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. To the extent possible, the same sets of ground motions as Experiment 2 were used in this experiment to evaluate the capability of the gap damper to limit the base-isolation system displacement during large ground motions. Each sine wave or earthquake motion was applied in a ramp-up sequence of increasing intensities building up to the maximum target identified in Experiment 2. The three earthquake motions selected for the test program were generally applied in a sequence and the gap damper device was recentered only at the end of the sequence.