Evaluation of design requirements for footbridges excited by vertical forces from walking

The continuing trend towards the design of more slender, lighter, and livel ier footbridges has created new challenges that are not properly addressed in a number of widely used codes of practice in Europe and Canada. Recent r esearch into vibration serviceability of slender structures under human-ind uced dynamic loading suggests that improvements to the existing footbridge design guidelines are possible in the area of modelling human-induced excit ation in the vertical direction. This paper evaluates the performance of cu rrently used codes of practice regarding vibration serviceability of footbr idges under human-induced loads due to walking. The evaluation is supported by experimental evidence from tests carried out by the authors on potentia lly lively footbridges. A description of recent research advances is includ ed, together with a comparative analysis of the approaches of some pertinen t guidelines used internationally to tackle this design problem. In additio n, suggestions are made for re-addressing the problem of vibration servicea bility of footbridges by focusing attention on a more realistic definition of vertical pedestrian loading and the corresponding frequency ranges of in terest. It was found that the codes are either conservative or lack appropr iate safety margins, depending on the frequency range excited by moving ped estrians. This is principally due to the lack of proper consideration for t he frequency content of the pedestrian load, which would take into account developments since the 1970s when the scientific data used in the majority of the current codes of practice were produced.