On Predicting the Ultimate Capacity of a Large-Span Soil–Steel Composite Bridge

The limit state design of large-span soil–steel composite bridges (SSCB) entails that understanding their structural behaviour in the ultimate state is as much needed as their performance under service conditions. Apart from box culverts, the largest loading-to-failure test was done on a 6.3-m span culvert. More tests on larger spans are believed essentially valuable for the development of the design methods. This paper presents the numerical simulation efforts of an 18.1-m span SSCB pertaining to its ongoing preparations for a full-scale field test. The effect of the different loading positions on the ultimate capacity is investigated. Comparisons are made between three-dimensional (3D) and two-dimensional (2D) models. The results enabled to realise the important role of the soil load effects on the ultimate capacity. It is found that the failure load is reduced when the structure is loaded in an asymmetrical manner. A local effect is more pronounced for the live load when the tandem load is placed closer to the crown. The study also illustrates the complex correlation between 3D and 2D models, especially if one attempts to simultaneously associate sectional forces and displacements.

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