설계변수의 효율적 가정에 의한 스트레스 리본 교량의 설계절차
vii, 191 p.
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Stress-ribbon bridges are the structures which resist to the majority of external forces with the axial force of the post-tensioned bridge deck produced by installing a very thin concrete deck on cables with a specific sag and by introducing post-tensioning forces to it. This concept was introduced for the first time in 1958 by Ulrich Finsterwalder for a long span bridge across the Bosporus(Festschrift, 1973). Stress-ribbon footbridges generally consist of bearing and post-tensioning cables as well as a concrete deck, and the ratio of the concrete deck depth(d) to the bridge length(L) is so small (d/L=0.0016-0.008) that the cable analysis and the membrane analysis can be allowed(Meguru et al., 1999). Despite of the much simpler composition than the general bridges, the complicated phenomena such as time-dependent behavior of creep and shrinkage, as well as the geometrically nonlinear behavior of deck and cable, should be considered in structural analysis. For general bridges, structural analysis and design can be accomplished only by the assumption of cross-section and the examination of the limit states of strength and serviceability. For stress-ribbon footbridges, on the other hand, in addition to the assumption of deck cross-section, the cross-sectional areas of bearing and post-tensioning cables and the post-tensioning force should be assumed because the behavior of stress-ribbon footbridges depends on that of cables of stress-ribbon footbridges. And in addition to the limit states of strength and serviceability, the achievement of the final targeted sag should be examined. As mentioned above, in the design of stress-ribbon footbridges more iterations are inevitable because it needs more assumptions and requires an additional design item to be examined than that of general structures. Even though various studies(Strasky, 2006, Codo del Arco et al., 2001; JPCEA, 2000) on the analytical model for the geometrical nonlinear cable behavior of stress-ribbon footbridges have been made, more researches on a design method to efficiently assume various design variables are still needed. Therefore, this study was done to present assumptive methods which can minimize iterations of the design process and make the design efficient as possible. Regression equations for the various design variables that can assume efficiently the cross sectional area of bearing and post-tensioning cables and the post-tensioning force were determined for the total nine footbridges with the bridge length of 40m, 80m and 120m applying the sag ratio of 1/50, 1/40, and 1/30 respectively, and the process of utilizing those was presented. Also, the maximum values for the cable stresses which are assumed for determining the cross-sectional areas of cables are determined for the total 12 footbridges with the bridge length of 40m, 80m, 100m, and 120m applying the sag ratio of 1/50, 1/40. and 1/30 so that the cross-sectional areas of cables can be minimized satisfying the strength limit state. It was proven through the two design examples for the stress ribbon footbridge of 100m length with the sag ratio of 1/30 that the presented assumptive method for the design variables was efficient in minimizing the iteration processes of design and in determining the cross sectional areas of cables and the post-tensioning force economically.