Structural behaviour and design criteria of under-deck cable-supported footbridges

The under-deck cable supported footbridges vary from under-deck cable-stayed bridges to under-deck suspensions bridges and stress ribbons, being all very effective and economic structures. The main reason for their efficiency is that they are working mainly under axial forces, taking advantage of the whole sectional area and thus leading to a significant reduction in the required materials. As a result, these structures can be very slender providing a satisfactory result in terms of aesthetic and sustainability. However, these types of footbridges, due to their slenderness, are quite susceptible to vibrations at the serviceability limit state. Several under-deck cable supported footbridges, such the Millennium Bridge in London, have had serviceability problems due to vibrations. That indicates that fundamental assumptions considered when developing load models, applied in their design, were not realistic. For that reason, a more detailed research of dynamic human-induced forces, human-structure dynamic interaction and pedestrian synchronization have been recently conducted [1]. The use of stochastic analysis for the estimation of these types of actions could have a significant impact in overcoming serviceability issues, leading to a more economic, sustainable and reliable design. The aim of this research project is to describe the static and dynamical structural behaviour of under-deck cable supported footbridge typologies and to propose design criteria for these structures. The study will be based on the FE models developed with Structural Analysis Software