Characterization and modeling of friction pendulum bearings subjected to multiple components of excitation

Experimental and numerical studies are used to examine the behavior of friction pendulum (FP) bearings to multiple components of excitation. In the experimental studies, a scaled rigid-frame model representing a rigid bridge superstructure on four FP bearings is subjected to displacement-controlled orbits and earthquake simulations. Using the test data from bidirectional displacement orbits, the constant friction coefficient is calibrated for a rate-independent plasticity model for FP bearings. The earthquake test data are compared with numerical simulations to evaluate the efficacy of the calibrated models. The studies show that the coupling between the two orthogonal components is important for representing the behavior of FP bearings. Modeling of the vertical load on the bearings, and the consideration of this force variation on the bearing response is necessary for an accurate determination of the forces transmitted by the bearings into the substructure. Tridirectional testing of the rigid-block frame shows that the vertical ground motion component has a small effect on the response of a bridge isolated with FP bearings.