Investigation of the relationship between bending capacity and SMFL intensity of existing reinforced concrete hollow slab beams.

• The magnetic parameter, concrete strain, reinforcement strain and deflection exhibit synchronous growth with high correlation. • The Y and B C curves in the mid-span of the beam effectively divide the beam failure mode into three loading stages. • The quantification of the relationship between mechanical indexes and SMFL intensity reveals linear associations for Y-B C and ε-B C. • A correlation between SMFL intensity, reinforcement stress and beam flexural strength is established. This paper proposes a novel approach for monitoring the bearing capacity of RC beams using the spontaneous magnetic flux leakage (SMFL) effect. Three decommissioned reinforced concrete hollow slab (RCHS) beams underwent bending loading failure experiments to collect data on crack formation, deflection Y , concrete strain ε , steel bar strain ε and SMFL intensity B x/y/z. The mechanical properties of concrete outside the structure and the magnetic properties of steel bars inside the structure during loading are investigated. The force-magnetic coupling effect of HRB400 steel bars is characterized. The SMFL parameter B C closely correlates with Y and ε variations in loading process, the quantitative relationship models between mechanical and magnetic parameters of the beam structures are established. A theoretical model predicted the ultimate bending capacity of RCHS beams. The relationship between beam bending capacity and SMFL intensity is clarified. [ABSTRACT FROM AUTHOR]