Kalman filter based estimation of neutral-axis position of bridge deck sections using strain monitoring data

The neutral-axis position has been recognized as a damage indicator for bridge deck assessment because of its high sensitivity to local damage on deck sections. It can be estimated when strain responses at the top and bottom of a deck cross-section under traffic loading are measured. However, the accuracy of neutral-axis position estimation directly using the measured strain responses might be significantly distorted in the presence of measurement noise and varying traffic load patterns. In this study, a Kalman filter (KF) estimator is formulated to locate the neutral-axis position from measured strain responses under traffic loading. Its capability for consistently locating the neutral-axis position under varying traffic load patterns is verified using the field monitoring data of traffic-induced strain responses acquired from the suspension Tsing Ma Bridge under diverse load scenarios (highway traffic, railway traffic, and their combination). The results indicate that the proposed KF estimator gives rise to consistent neutral-axis position estimation results which are independent of load conditions and patterns.