Investigation of SMFL monitoring technique for evaluating the load-bearing capacity of RC bridges

Abstract

This study investigates the use of Self-Magnetic Flux Leakage (SMFL) monitoring to assess the load-bearing capacity of RC bridges under vehicular loading. Cyclic tensile experiments of HRB400 rebars were conducted and the SMFL intensity was monitored. The integrated vector value of SMFL intensity BC was introduced to analyze the characteristics of the rebar force-magnetic coupling effect. Moreover, SMFL monitoring experiments were conducted on Gaojia Garden Bridge to evaluate the engineering applicability of the method. The results show that the mechanical indexes have a positive correlation with SMFL intensity during rebar cyclic loading. The increase in the cycle number drives the stability of the force-magnetic relationship. The rebar proportional ultimate strength σpl is an important factor affecting the BC variation. When the stress exceeds σpl, the rising process of BC curve retreats. The rebar stress range can be accurately determined based on the change rate of SMFL intensity. In the testing of Gaojia Garden Bridge, vehicles loading and unloading contribute to the phased increase and monotonic decrease of BC curves, respectively. Comparing the FEM simulation results, the linear characteristic relationships between BC and |με| as well as σ are obtained, which verifies the engineering applicability and accuracy of SMFL monitoring method. This research provides a new approach for the non-destructive quantitative detection and test application of RC bridge load-bearing capacity.