A tiered approach to the fatigue assessment of composite steel and concrete bridge beams

Abstract

The behaviour of composite steel and concrete beams subjected to fatigue loads is complex due to the slip between the steel and concrete components that is required to load the mechanical shear connectors and which is found to change continually with time. Most new designs are based on a generally conservative assumption of full interaction; however, in the assessment of existing structures, and in order to reduce costs, it is often necessary to use the bridge to its full potential, which requires advanced analysis techniques that allow for interface friction and partial interaction. A tiered approach to assessment of simply supported beams is described that starts with a simple but conservative assessment and gradually increases in complexity and accuracy. For example, if the first simple assessment finds the structure inadequate then the complexity of the analyses can be gradually increased to extract more of the potential strength and endurance. Should the full potential of the structure still be found to be inadequate, then this tiered approach can also be used in the assessment of the effect of remedial measures.