Tensegrity Footbridges with Arch and Straight Deck: Comparison of their Structural Behaviour

The design of two types of tensegrity footbridges, made of struts (deck and vertical columns) unconnected one to the others (as required to tensegrities), and ties (cables), is introduced. In both cases, the deck is suspended between upper and bottom main cables, and is equidistant from them. In the first case, the footbridge is symmetric with respect to the horizontal deck, while in the second case the deck is arched, so that the bottom main cables are less curved then the upper ones. Since cable pretension results in strut prestressing, then both types of decks result to be prestressed, thus avoiding that high tensile forces in the main cables are transferred to embankment foundations. Taking into account geometric nonlinearity, static and dynamic behaviour of both types of tensegrity footbridges are analyzed by finite elements. Structural behaviour of bridges in tensegrity appears to be suitable for footbridges, although peculiar with respect to traditional ones. Some suggestions about structural design are finally summarized