Application of non-linear multiple tuned mass dampers to suppress man-induced vibrations of a pedestrian bridge

摘要

This paper presents an application of multiple tuned mass dampers (MTMDs) with non-linear damping devices to suppress man-induced vibrations of a 34m long pedestrian bridge. The damping force generated by each of these damping devices is simply a drag force from liquid acting on an immersed section. The quadratic non-linear property of these devices was directly determined from free vibration tests of a simple laboratory set-up. Dynamic models of the bridge and pedestrian loads were constructed for numerical investigation based on field measurement data. The control effectiveness of non-linear MTMDs was examined along with its sensitivity against estimation errors in the bridge's natural frequency and magnitude of pedestrian load. The numerical results indicated that the optimum non-linear MTMD system was as effective and robust as its linear counterpart. Then, a six-unit non-linear MTMD system was designed, constructed, and installed on the bridge. Field measurements after the installation confirmed the effectiveness of non-linear MTMDs, and the measurement results were in good agreement with numerical predictions. After the installation, the average damping ratio of the bridge was raised from 0.005 to 0.036 and the maximum bridge accelerations measured during walking tests were reduced from about 0.80-1.30 ms~(-2) to 0.27-0.40 ms~(-2), which were within an acceptable range.