Response estimation for a floating bridge using acceleration output only

The Norwegian Public Roads Administration is reviewing the possibility of using floating bridges as fjord crossings. The dynamic behaviour of very long floating bridges with novel designs are prone to uncertainties. Studying the dynamic behaviour of existing bridges is valuable for understanding the in-situ performance. We present a case study of the Bergsøysund Bridge, a 840 m long floating pontoon bridge located in Norway. An extensive monitoring system is installed on the bridge, including a network of accelerometers. A finite element model of the bridge is established. Using the measured acceleration output and recently developed Kalman filter based methods (a joint input-state (JIS) estimation algorithm and a dual Kalman filter (DKF)), we estimate accelerations at unmeasured locations. It is shown that the estimated response from the DKF agrees well with direct reference measurements. For the JIS, numerical instabilities in the estimates occur due to ill-conditioning of the matrices used in the system inversion.