The need of exploring efficient solutions to today’s engineering problems is becoming essential in the current market development. Soil Steel composite bridges (SSCB) are considered well competitive in terms of their feasibility and constructability. The primary objective of this study is to provide a comprehensive comparison study for two known design methods of SSCB, which are the Pettersson-Sundquist design method (developed in Sweden) and the Klöppel & Glock design method (developed in Germany). Moreover, in the goal of having better behaviour understanding for SSCBs, the study also include finite element modelling (FEM) using PLAXIS 2D of three case studies and compare model results with field measurements.   The design comparison deals with the design concepts, assumptions and limitations for both design methods, where full design procedures are implemented and compared for a defined case study.   The results of the FEM analysis show rational outcome to the field measurements for structural response during backfilling and close results for ordinary loading as well. While the design comparison shows how the different approach in both design methods in limitations and design assumptions has important impact on the results, where soil failure in the Klöppel & Glock design method can be controlling the design for low heights of cover, whereas formation of crown plastic hinge is more controlling in the Pettersson-Sundquist design method. However, and in general, the Pettersson-Sundquist design method require more steel in low heights of cover while it is less demanding for higher soil covers compared to the Klöppel & Glock design method.

Although the construction of flexible culverts involves simplicity in comparison to similar concrete structures, the complexity of the beneficial interaction between soil and steel materials requires good understanding for their composite action and performance. Current design methods have certain validity limitations with regard to applicable slopes above the structures. Given the short construction time of flexible culverts, there is an urge to explore the feasibility and the constructability of such as cost-effective structures in sloping terrain, where they may function as an avalanche protection structure for a given road, a culvert under a ski slope, or even as a protection canopy for tunnel entrances. This report compiles the efforts carried out toward gaining knowledge about the different factors that may affect the behaviour of flexible culverts in sloping environment. The report includes an extended summary of the investigation, which is mainly presented in two appended papers. The study involved numerical simulation of three case studies to investigate their performances with regard to soil loading and avalanche loads as well. The height of cover, surface slope intensity, slope stability, soil support conditions, and avalanche proximity, were studied and discussed. The study results allowed realizing the susceptibility of flexible culverts to low heights of soil cover when built in sloping terrain, which is reflected in the deformation response and the incremental change in sectional forces, especially the bending moments. It is also found that increasing the depth of soil cover may feasibly improve the structural performance under asymmetrical soil loading and avalanche loads, where it subsequently help in reducing the bending moments in the wall conduit. The presence of a flexible culvert may affect adversely the soil stability in sloping terrain and thus need to be addressed in design. Furthermore, the flexural response of a flexible culvert is directly influenced by the soil support configuration at the downhill side of the structure. In addition, the report also attempts to highlight some general guidelines about the design aspects of flexible culverts in sloping terrain, and seeks to reflect some of the findings on the design methodology for flexible culverts used in Sweden. / <p>QC 20151130</p>