Efficient assumption of design variables for stress ribbon footbridges

Abstract

The design of stress-ribbon footbridges needs more iterations than the design of general structures. This is because, in addition to the cross section of deck, the cross sectional areas of bearing and post-tensioning cables and the post-tensioning force should be assumed. To minimize the iterations in this study, the regression equations of design variables, which can reasonably assume the cross sectional area of bearing and post-tensioning cables and the post-tensioning force, are determined for various bridge lengths with varying sag/span ratios. Also, the maximum values for the cable allowable stresses, assumed to determine the cross sectional area of cables, are presented for various bridge lengths with various sag/span ratios. It is demonstrated through the design examples that the suggested preliminary design method assuming design variables is efficient in minimizing iterations of the design process for single-span and multi-span stress-ribbon footbridges and in determining the cross sectional areas of cables and the post-tensioning force economically.