Rolling Load versus Pulsating Load Fatigue Behavior of a Full-Scale Bridge Deck Reinforced with GFRP Bars

This paper presents a pioneering experimental investigation of the fatigue behavior of a full-scale (15.24 m × 3.89 m) concrete bridge deck reinforced with glass fiber–reinforced polymer (GFRP) rebar under rolling (R)-load cycles applied using the Rolling Load Simulator (ROLLS) at Queen's University, Canada. The study compares this type of fatigue with conventional fixed-point pulsating (P)-loads. The deck is supported by two Steel I-girders spaced at 3.05 m. A 3.81-m-long section on one end was subjected to R-loads and a similar section on the other end, to P-loads, both up to 3 million (M) cycles. Monotonic tests were performed periodically. The study showed that R-load results in far more fatigue damage than P-load, as reflected by 71% and 54% stiffness degradation (k/ko), respectively. This suggests that cumulative damage of one R-cycle is equivalent to 120 P-cycles. Live load deflection limit of span/800 was reached in the R-loading section after 0.78M cycles, and at 3M cycles was exceeded by 15%, but the P-loading section remained below the limit. GFRP reinforcement performed very well, with maximum strain remaining below 10% of the guaranteed tensile strain. The R-load section showed far more extensive and dense grid-pattern cracking with concrete pitting at the soffit, while the P-load section showed minor longitudinal and some radial cracks. A conversion factor (ξ) is established to enable researchers and designers convert (k/ko) from readily and easily available P-loading to an equivalent R-loading of GFRP-reinforced deck at any number of cycles, since P-loading is not conservative and R-loading capabilities are not easily available. In this study, ξ is 0.59 at 3M cycles and is projected to be 0.5 at 10M cycles.