Strategies to improve the structural integrity of tied-arch bridges affected by instability phenomena

A numerical study is proposed to investigate the nonlinear behavior of steel tied-arch bridges, whose arch ribs are inclined inwardly. The main aim of the paper is to assess if the arch rib inclination may be an effective strategy to enhance the structural integrity of the bridge structure against out-of-plane buckling mechanisms. The nonlinear behavior of the structure is investigated throughout an advanced 3D finite element model, which accurately reproduces nonlinear sources involved in the cable system and structural elements. An analysis that combines results obtained by traditional elastic buckling analysis and incremental nonlinear elastic analysis is employed to properly evaluate the maximum capacity of the structure. Comparisons between bridge structures with inclined and vertical ribs configurations are proposed focusing attention on both structural and economic aspects. Results show that rib inclination provides several structural benefits to the bridge while reducing overall construction costs.