Network Arches: The World's Lightest Arch Bridges

Abstract

Summary Network arches have a tensile and a compressive flange with a web consisting of crossing hangers. Some of the hangers cross each other twice. The network can be seen as a very light, simply supported beam. There is little bending. There is a lot of tension in tie and hangers. The arches are well supported by hangers and wind bracing. Thus the buckling strength of the arch is high as long as few hangers relax. That is easiest to prevent when a concrete tie gives extra weight in the tie. The optimal shape of network arches is discussed. In two lane and two track network arches the biggest bending in the tie is usually the transverse bending half way between the arches. The optimal shape of network arches is discussed at length. The axial force between the ends of the arches is best taken by prestressing cables. Pontoons or big cranes can move a network arch to the pillars after it have been built somewhere else. The weight to be moved is much lighter if it consists of the structural steel, plus a temporary lower cord that can carry the casting of the concrete tie. This steel skeleton can also be built on ice in the winter and be lifted onto the pillars. The concrete tie can be cast in the spring. The author came to think of the network arch when he was doing his master thesis in 1955. Till now around 100 network arches have been built in over 20 countries. There is a lot of information on network arches attached to the author’s home page http://home.uia.no/pert and in Tveit (2008).