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Progressive collapse in long-span cable-supported bridges
Citation Link: https://doi.org/10.15480/882.3016
Publikationstyp
Doctoral Thesis
Date Issued
2020-10-13
Sprache
English
Author(s)
Advisor
Starossek, Uwe
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2020-09-15
Institut
TORE-DOI
TORE-URI
Citation
Technische Universität Hamburg (2020)
Publisher
epubli
Parallel load-bearing systems are structural systems with load-bearing members that are similar in type and function and constitute alternative load paths. Cable-supported bridges are good examples of such a structural system. In the case of the failure of one of the parallel load-bearing elements (cables), the load carried by the failed member must be redistributed to the remaining structure. In this situation, the member adjacent to the failed member receives most of the redistributed load and becomes the critical member. If this member cannot tolerate the redistributed load, the collapse can progress to the subsequent members and, possibly, the entire
structure. Hence, because of the vital role of the critical member in the robustness of the structural system, the focus of this study is mostly on this member. In this study, a parallel-load bearing system is considered as a conceptual model of long-span cable-supported bridges. The target is to calculate the “stress increase ratio” of the critical cablen a cable-loss scenario. The structural characteristics of the system, including the bending stiffness of the girder and a unique axial stiffness in each cable, have been taken into account. The failure of several cables has also been considered. An analytical approach based on differential equations of the system has been used, and an approximation function for the calculation of the stress increase ratio of the critical cable in a cable-loss scenario has been derived. The least squares method has been applied to minimize the error of the approximation function. The results show that by increasing the ratio of the bending stiffness of the girder to the axial stiffness of the cables (β-value), the stress increase ratio of the critical cable decreases. The acceptable accuracy of the presented approximation function has been proved by the comparison of the exact stress increase ratio values, and the one calculated from the proposed approximation function. Except for small β-values, the error of the proposed approximation function is less than 5% in the investigated systems. The developed approximation function has been used to derive a reserve-based robustness index. Besides, the structural robustness of a system segmented by zipper-stoppers has been investigated, and the stress increase ratio of the zipper-stopper in a cable-loss scenario has been examined. In addition, a similar approach for the calculation of the increase of maximum bending moment on the girder due to cable failure has been performed. The results show that by increasing the β-value, cable failure produces a larger bending moment on the girder. This means that for systems
with smaller β-values, bending moments are smaller. Finally, a practical method for the optimization of cable distance in cable-supported bridges has been developed, and the optimum design of cable-supported bridges considering the failure of several cables has been investigated. The method minimizes the cost of bridge construction and guarantees a certain level of robustness.
structure. Hence, because of the vital role of the critical member in the robustness of the structural system, the focus of this study is mostly on this member. In this study, a parallel-load bearing system is considered as a conceptual model of long-span cable-supported bridges. The target is to calculate the “stress increase ratio” of the critical cablen a cable-loss scenario. The structural characteristics of the system, including the bending stiffness of the girder and a unique axial stiffness in each cable, have been taken into account. The failure of several cables has also been considered. An analytical approach based on differential equations of the system has been used, and an approximation function for the calculation of the stress increase ratio of the critical cable in a cable-loss scenario has been derived. The least squares method has been applied to minimize the error of the approximation function. The results show that by increasing the ratio of the bending stiffness of the girder to the axial stiffness of the cables (β-value), the stress increase ratio of the critical cable decreases. The acceptable accuracy of the presented approximation function has been proved by the comparison of the exact stress increase ratio values, and the one calculated from the proposed approximation function. Except for small β-values, the error of the proposed approximation function is less than 5% in the investigated systems. The developed approximation function has been used to derive a reserve-based robustness index. Besides, the structural robustness of a system segmented by zipper-stoppers has been investigated, and the stress increase ratio of the zipper-stopper in a cable-loss scenario has been examined. In addition, a similar approach for the calculation of the increase of maximum bending moment on the girder due to cable failure has been performed. The results show that by increasing the β-value, cable failure produces a larger bending moment on the girder. This means that for systems
with smaller β-values, bending moments are smaller. Finally, a practical method for the optimization of cable distance in cable-supported bridges has been developed, and the optimum design of cable-supported bridges considering the failure of several cables has been investigated. The method minimizes the cost of bridge construction and guarantees a certain level of robustness.
Subjects
Progressive Collapse in Long-Span Cable-Supported Bridges
DDC Class
690: Hausbau, Bauhandwerk
More Funding Information
DAAD
Publication version
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