Assessment of the Dynamic Structural Response of Footbridges Subjected to Vandal Loads: Numerical and Experimental Modelling

This research work aims to investigate the dynamic structural behaviour of pedestrian footbridges, when subjected to dynamic vandal loadings, based on the development of experimental tests and numerical modelling. The investigated footbridge is associated to a simply supported concrete structure with span of 24.4 m, currently used for pedestrian crossing, and located at the Faculty of Engineering (FEN) of the Rio de Janeiro State University (UERJ). Having in mind the strategic location of the footbridge, near the FEN/UERJ Director’s office, different loading scenarios were idealized to carry out experimental forced vibration tests on the structure, with the participation of up to 20 people, aiming to simulate dynamic vandal loads. Initially, an experimental modal analysis was performed on the investigated footbridge, in order to identify and assess the global dynamic behaviour of the system. In sequence, a finite element model was developed and calibrated through experimental results. After that, based on the forced vibration experimental tests the footbridge dynamic response was assessed. According to the results of this investigation, for the cases of 15 and 20 people exciting the footbridge (vandal loads), the peak accelerations are, respectively, 1.30 m/s² and 1.60 m/s², and excessive vibrations and human discomfort can occur. Finally, it must emphasised that the analysed footbridge should only be used to human walking.