Test up to ultimate limit state and failure of innovative prebended steel-VHPC beams for railway bridges in France

Experimental validation of a possibly attractive extension of the pre-bended composite beams technique, first applied in Belgium as “Preflex”, was carried out. Very high performance concrete (C80/95) was used for potential advantages of low delayed strains and high tensile strength. A major issue of the programme consisted in validating a design method for the serviceability limit state (SLS) linked to the cracking of the concrete and for the ultimate limit state (ULS) corresponding to an instability (warping) or to yielding of the steel girder. Detailed results of the global response of two 13 m-long beams up to ultimate limit state and failure are analyzed in conjunction with deflection measurements. The ultimate limit state computation based on the strength and elastic stability is always controlled by the serviceability limit state for this kind of structures.