HYBRID TESTING WITH MODEL UPDATING OF A BRIDGE WITH SEISMIC ISOLATION INCORPORATING ROTATION

Most current numerical models for isolation bearings assume parallel end-plate conditions neglecting bearing rotations. However, bridges with flexible piers and spans can lead to rotational demands, invalidating this assumption, yet experimental testing of the interaction of bearing with rotation within the system would be cost prohibitive. As such, a large-scale hybrid simulation was completed using a model of a multi-span, major toll bridge with seismic isolation lead rubber bearings located on top of flexible piers located in California. As the behavior of the bearing under rotation and the coupling between the shear and rotational behavior is less well known, a one third scale lead rubber bearing was used as the experimental element. The remainder of the bridge, including the bearings in the remaining twelve piers were numerically modeled. To ensure that the remainder of the bearings were accurately represented, online model updating was employed during the testing. Model updating can enhance hybrid simulation by utilizing the experimental data from the physical specimen to update numerical elements with similar characteristics. A weighted adaptive constrained unscented Kalman filter was used for the model updating algorithm, and it is shown to accurately capture the bearing behavior observed experimentally under axial, shear, and rotational demands. The testing explored both how to best conduct the hybrid test with model updating as well as the effects of including rotational behavior on the global bridge performance.