Coincidence of structure and walkway as an inspiration for footbridge design

The higher longitudinal slopes allowed by pedestrian traffic if compared with road or railway ones, and the occasional or sometimes essential need to include stairs as members of a pedestrian crossing, make it possible for footbridges to have a higher grade of geometrical coincidence between their main structural elements and their walking surfaces than other bridge types, beyond the obvious case of the beam-bridge scheme. There are well-known paradigmatic examples of historic passable arches and catenaries, basic bridge types with full (or almost full) coincidence of structure and walkway. During the last 15 years, contemporary versions of these basic types as well as halfway or hybrid solutions have used the geometrical flexibility inherent to pedestrian bridges as a source of inspiration itself, sometimes achieving innovative designs and becoming really valuable findings.

Coincidence between structural elements and walkways can lead to brilliant designs, full of visual content, structurally coherent and economical, which brilliantly take advantage of the possibilities offered by footbridge design parameters... or to arguable solutions where formal aims cause malfunctions in terms of utility, which jeopardise the global quality of the crossing concept.

The objective of this paper is to show how the possibility of coincidence between structure and walkway has become a recent source of inspiration in the search for new aesthetic and structural schemes, as well as to analyse the real grade of success and failure of this achievements as appropriate solutions for a crossing problem.