Experimental study on fatigue behaviour of orthotropic steel decks under traffic loads

Orthotropic Steel Decks (OSDs) are widely used in modern bridge construction for their lightweight and high-strength properties, yet they face significant fatigue challenges under dynamic loading. This paper presents an experimental investigation into OSD fatigue performance using a sequential, multi-position loading protocol. Focusing on strain and deflection measured through strain gauges and linear potentiometers, a scaled-down specimen was developed to analyse stress distributions and identify fatigue-prone areas. The findings revealed significant strain concentrations at rib-to-deck connections, identifying them as key locations for early plastic deformation and fatigue damage initiation. Additionally, rib-to-diaphragm (RTD) connections exhibited elevated fatigue sensitivity, indicating complex load transfer mechanisms and non-uniform stress distribution across the deck. The main highlight of this paper lies in its sequential loading protocol and detailed monitoring strategy, which accurately approximate the spatial variability of in-service traffic compared to conventional single-point static approaches. By comparing these findings with existing research, the paper highlights the specific fatigue challenges associated with dynamic traffic loading and contributes to a deeper understanding of fatigue-resistant mechanisms in long-span steel bridges. These insights provide a useful basis for informing the development of monitoring and fatigue-assessment strategies for long-span OSD structures.