A method for the robustness evaluation of cable-stayed bridges with steel truss girders under different reinforcement cases

Structural robustness, an index for structural geometrical agreement, is used to assess the alternative load paths of structures subjected to loads. Therefore, robustness can be extended to evaluate the robustness of bridges with local failure in individual members. In this work, a method that includes the use of a radar chart is proposed to assess the robustness of cable-stayed bridges by considering the mechanical performance of bridges with local failure in the cables and chords. Four plans regarding the truss girder and cables are designed to reinforce a damaged bridge. The results indicate that these two alternative path plans disperse the stress in the members in the truss girder, and the reduction of alternative path plan 2 (AP2) is greater than that of alternative path plan 1 (AP1). Similarly, the two plans regarding the cables are found to decrease the vertical displacement of the truss girder under gravity, and the reduction of the first plan is slightly greater than that of the second plan. Consequently, the two alternative load path plans improve the indexes of the truss girder, leading to an increase in the value of IRob to 0.74. Moreover, regarding the truss girder, the two alternative cable plans are used to increase the indexes, and the values are all found to be larger than the corresponding values of the intact cable-stayed bridge. The proposed method including the use of a radar chart, which is associated with several indexes, can be used to assess the structural robustness of intact and damaged bridges, thereby allowing for the development of reinforcement plans.