Stress Ribbon Bridges: Mechanics of the Stress Ribbon on the Saddle

Abstract

The most slender and flexible footbridges are stress ribbon bridges. One kind of these elegant and simple bridges consists of two hanging steel ribbons, usually made of steel, which carry concrete deck panels and are anchored between two heavy abutments. At the anchorage and on intermediate supports the ribbons are often supported by saddles that are curved so that the additional bending stresses in the ribbon, which occur there, stay within allowable limits. The magnitude and the distribution of the bending stresses, the transverse pressure the ribbons exert on the saddle, and stress changes in the region of the detachment point caused by live loads are crucial for the dimensioning of these ribbons. A clear understanding of these issues via parametric studies, analytical solutions, and confirmation by finite-element (FE) analyses are provided in this paper. The findings presented here can also be used for other saddle systems, such as those used in cable-stayed and extradosed bridges.