Quantifying fatigue damage in reinforced concrete beams through piezomagnetic effect: A fatigue-magnetomechanical coupling approach

As a ferromagnetic material, steel ribbed bars exhibit spontaneous magnetisation due to the piezomagnetic effect under cyclic loading. Previous studies have demonstrated the use of piezomagnetic signals to characterise fatigue damage in steel bars. However, a quantification model for fatigue damage in reinforced concrete components based on the piezomagnetic effect is currently lacking. This study introduces a fatigue-magnetomechanical coupling model tailored for reinforced concrete beams under cyclic loading, accounting for fatigue damage in both the steel reinforcement and concrete. The fatigue life and failure modes of reinforced concrete beams, along with the magnetisation of the reinforcement, were simulated and compared with experimental results. The results show that the modified model effectively captures the evolution of magnetisation in reinforced concrete beams subjected to cyclic loads. Utilising the results derived from electron microscopy scanning and the established fatigue-magnetomechanical coupling model, the mechanism by which fatigue damage in the reinforcing steel within concrete beams influences magnetic field variations has been elucidated. In the end, the fatigue damage in reinforced concrete beams is quantified by using simulated magnetisation intensity and experimentally measured piezomagnetic signals.