Considerations for Design of Network Arches

Abstract

Network arches can be defined as those with inclined hangers with multiple intercetions. In network tied arch bridges, the arch and the tie can be made more slender than in other arch bridges. The tie is usually a concrete slab roadway with longitudinal prestress. For load cases that relax a few hangers, network arches act very much like trusses. Thus, they have little bending in the tie and the arches. To avoid relaxation, the hangers should not be inclined too steeply. Too small an inclination of the hangers will increase the bending moments due to concentrated loads. Compared with similar spans of conventional steel bridges, the network arch usually saves half the weight of steel. During erection, the arch and hangers, supplemented by a light lower chord, can support a concrete roadway while it is being cast. The network arch is most appropriate when local conditions lead to acceptance of structural members above the roadway. This seems to occur more often for railway bridges than for road bridges.