Control of Human-Induced Vibrations of a Curved Cable-Stayed Bridge: Design, Implementation, and Field Validation

Abstract

This article describes the research work relating to the assessment and control of human-induced vibration of an unusual curved cable-stayed bridge with separate road and pedestrian decks. Dynamic simulations of human-induced vibration were performed with a mode-by-mode approach, and the results showed that a total of eight lateral and vertical modes of the bridge may suffer from excessive vibrations at the design crowd density. A hybrid control scheme was developed for control of human-induced vibration, which consists of steel braces fitted between the road bridge deck and the pedestrian deck to improve structural stiffness and eddy current tuned mass dampers to enhance damping ratios of lively modes. The modal properties of the bridge with steel braces were experimentally obtained by dynamic tests and used for parameter tuning of mass dampers. The performance of the hybrid control strategy was evaluated by group tests of up to 400 pedestrians. It is shown that the critical number of pedestrians triggering synchronous lateral excitation is generally in good agreement with the empirical model developed from measurements on the London Millennium Bridge, but the measured vertical acceleration amplitude is only about 40% of the prediction under the same pedestrian density. The damping ratios for both the vertical and lateral modes increase appreciably after installation of tuned mass dampers and no evidence of large-amplitude vibrations has been observed.