Shake table tests of different seismic isolation systems on a large scale structure subjected to low to moderate earthquakes

Seismic isolation systems designed for extreme events may likely experience low to moderate earthquakes during the design life of the structure rather than the extreme event itself. In new seismic building design codes, low and moderate earthquakes are also mandatory to be investigated in Turkey and some other countries. One of the main reasons is to protect the integrity of non-structural elements or machines during these types of earthquakes. The selection of appropriate seismic isolation is typically decided based on their force-displacement characteristics and amount of energy dissipation per cycle. The same energy dissipation per cycle (EDC) can be achieved by high force-low displacement or low force-high displacement response. The focus of this research is given to identify the performance of ball rubber bearing isolation systems compared to different or similar EDC units such as elastomeric bearings and lead rubber bearings through a series of shake table tests performed at low to moderate earthquake levels. Shake table tests were conducted on an almost full scale short span bridge. The tests have revealed that the ball rubber bearings are superior to elastomeric bearings in terms of EDC and can match EDC of LRB. However, although LRB and BRB have the same EDC, BRB is more beneficial to use under low to moderate earthquakes since BRB can transmit less force with larger displacement compared to LRB and LRB can sometimes stay in elastic range with an ineffective EDC as a stiffer elastomeric bearing. •Ball rubber bearings provide the same EDC as lead rubber bearings while having less stiffness.•Ball rubber bearings transfer smaller forces to substructure elements than lead rubber bearings do.•Ball rubber bearings have both larger EDC and stiffness compared to elastomeric bearings.•Ball rubber bearings lead to a more significant improvement in seismic response compared to elastomeric bearings.