Benchmark structural control problem for a seismically excited highway bridge-Part III: Phase II Sample controller for the fully base-isolated case

This paper presents the fully base-isolated highway bridge benchmark problem. The highway bridge benchmark problem consists of two phases: (1) Phase I—the bridge deck being base isolated only at the abutments and the center bent being integral with the pier (without isolation), and (2) Phase II—the bridge deck being fully base isolated at both the bent/pier and abutment locations. In both phases of the highway bridge benchmark, the objective is to augment the performance of the isolation system using supplemental control strategies. The problem definition (Part I) as well as a sample controller (Part II) for Phase I of the study has been presented in the companion papers. The focus of this paper is to present the fully base-isolated highway bridge and sample Lyapunov semiactive controller (Part III). As-built structural designs of the 91/5 overcrossing in Orange county in Southern California are used to develop the finite-element model for this benchmark based on Phase I. The nonlinear analysis tool and the controller interface have been developed in MATLAB. The bridge is isolated using nonlinear elastomeric bearings with a lead core. Magneto-rheological (MR) dampers are used to control the seismic response of the bridge. The MR dampers are installed at the isolation level at 10 locations over the abutments and bent/pier locations, each location consisting of an orthogonal pair of dampers to control the responses in both directions. The outputs allowed in the benchmark problem definition are used to design the controller and the velocity and displacement measurements if required are obtained by integrating accelerations using a filter, which simulates integration. Detailed comparisons of benchmark performance indices for the fully base-isolated bridge with sample semiactive controllers and passive strategies are performed in comparison with the uncontrolled case, for a set of strong near-field earthquakes. The sample Lyapunov semiactive controller is shown to reduce the isolator and mid-span displacements. The modeling and sample control designs demonstrated in this paper can be used to form the basis for studying a wider variety of active and semiactive control strategies—to be developed by the participants in the benchmark study—for fully base-isolated highway bridges. Copyright © 2009 John Wiley & Sons, Ltd.