Dynamic Analysis of Suspension Footbridges Using an Actual Pedestrian Load Model Compared with EUR23984 EN Requirements

Abstract

The suspension footbridges are very flexible due to their geometrical structure; hence they may face severe vibration problems induced mainly by natural forces and pedestrians crossing. By exceeding a certain limit, these vibrations can disturb the serviceability of the bridge as well as health and safety of the structure and pedestrians. Therefore, standard design guidelines are sets of recommendations to control the vibrations by applying restrictive design criteria. Because of the complexity of the exact simulation of the human-induced loads, these guidelines provide simplified methods to cover the frequency ranges of the human motion types in order to estimate the response of the structure without modeling the actual motion. As current paper, the simplified loading method proposed by EUR23984 EN code‑as the main footbridge design standard was investigated. Its compliance with pedestrian's synchronization phenomenon was evaluated using the analysis results of a discontinuous type loading model proposed by authors. It was shown that the response of the footbridge strictly depends on the type and the speed of the pedestrian motion applied to the bridge, which is not included in the design parameters of the code. In this research work, a series of analysis is conducted on a suspension footbridge as a case study under both actual human loads and the simplified loads suggested by the code and the results were compared. It was found out that in the same crowd loading, the actual human loading creates greater vertical accelerations compare to EUR 23984 EN method results.