Transient response simulation of a composite material footbridge to crossing pedestrians.

Abstract

Loads applied by pedestrians, and crowds of pedestrians, are particularly important for footbridges with natural frequencies close to footfall frequencies of moving pedestrians. Recorded response data from Aberfeldy Bridge, an advanced composite material footbridge in Scotland, for numerous pedestrian crossings reveal both vertical and lateral response components. No provision is made in existing codes of practice for the calculations of actual dynamic responses in pedestrian footbridges to lateral pedestrian-induced load. The authors are seeking to develop an appropriate pacing frequency-dependent lateral load model, to be used in conjunction with existing vertical loads models that wold account for such lateral excitation. This is done by correlation of the measured bridge dynamic response with the results of the simulations where a validated numerical model has been utilised. The modelling techniques used to correlate the modal properties of the finite element model with the real structure are described in this paper, Subsequently the modelling and transient solution strategies used to simulate the vertical footbridge response at different pacing frequencies are compared to actual bridge measurements to good effect,. Finally a structure for the form of the lateral load model required to capture pacing frequencey dependent lateral effects is also proposed.