Seminar reviews are written by graduate students in the school of engineering. The stability of seismic isolation bearings was the subject of the seminar presented on March 7 by Dr. Satish Nagarajaiah, who is currently an assistant professor of civil engineering at the University of Missouri, Columbia. This seminar attracted 45 attendees including students and professors. When isolation systems are used in structures, they introduce flexibility and thus increase the fundamental frequency of the structure. A base isolated structure therefore has a longer period than a fixed base structure.
Elastomeric bearings are just one of the isolation systems currently being used.
They are laterally flexible due to their low shear stiffness. During a strong earthquake, larger lateral displacements and axial loads occur. These then cause P-delta effects in the bearings. It is therefore important to consider these effects when analyzing and designing the bearings due to concerns about stability under large displacements. This issue was the focus of the presentation.