Design and Performance of a Tuned Vibration Absorber for a Full-Scale Lightweight FRP Pedestrian Structure

Abstract

Fiber-reinforced polymers (FRPs) have enabled the construction of lightweight footbridges, whose structural design is often governed by a serviceability limit state. A suitable approach to avoid overdimensioning an FRP footbridge may be to adopt a motion-based design strategy, where excessive human-induced vibrations are mitigated through the installation of tuned vibration absorbers (TVAs). In this sense, human–structure interaction (HSI) phenomena should be considered to estimate accurately the acceleration response of lightweight footbridges and size TVAs properly. Thus, this paper presents the design, installation, and performance assessment of a passive inertial controller for completing the construction of a full-scale FRP pedestrian structure. First, a general frequency-domain procedure to design TVAs for structures susceptible to HSI is proposed. The methodology considers a multiobjective optimization problem that minimizes simultaneously the structural response and the controller inertial mass. Second, the HSI load model of a bouncing pedestrian is identified experimentally to be used within the proposal to design TVAs. Third, a TVA of 25 kg is designed, assembled, and installed in the lightweight FRP structure, employing the proposed procedure. Then, the enhancement of the dynamic response due to the controller is assessed considering a person bouncing and two streams of walking pedestrians. For the different load scenarios, the TVA exhibits an adequate behavior to mitigate the vertical acceleration, demonstrating the feasibility to deliver an ultralightweight FRP footbridge with an inertial controller to meet requirements at different limit states.