Experimental tests demonstrate improved fatigue performance of retrofitted composite girders, suggesting the need for pre-fatigue condition considerations.
Understanding the fatigue behavior of retrofitted beams in bridge structures is vital. The effects of pre-fatigue conditions on the efficacy of retrofitting tend to be overlooked. In this paper, five samples were experimentally tested under fatigue. The effects of external retrofitting on the cyclic crack patterns on the concrete flanges, cyclic incremental deformations, and strains were investigated with various pre-fatigue conditions. The pre-fatigue conditions included exposure to outdoor environmental changes, plastic deformations, and fatigue damage. The results showed that external PT enhanced the performance of the individual components of the composite samples, which improved the overall fatigue performance of the strengthened samples. However, the strengthened samples experienced longitudinal fatigue cracks in the concrete flanges because of post-tensioning. The pre-damage condi-tions due to fatigue loading and environmental changes caused greater damage in concrete around the studs relative to the plastically pre-deformed strengthened sample and led to more incremental de-formations and strains.
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Alsharari et al. (2025) studied this question.
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