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This paper presents a nondestructive test method to evaluate the residual bending strength of corroded reinforced concrete beam by analyzing the self-magnetic flux leakage (SMFL) signals. The automatic scanning device was equipped with a micromagnetic sensor and sensor-based experimental details were introduced. Next, the theoretical formula of the normal component HS(z) of the SMFL signal that originated from the corroded region was derived based on the magnetic dipole model and the experimental results were discussed. The results indicate that the experimental data of HS(z) are consistent with the theoretical calculations, both location and extent of the steel bars corrosion can be qualitatively determined by using HS(z). The gradient K of HS(z) is approximately linearly related to the loss rate, S, of the bending strength, which can be used to evaluate the residual bending strength of the corroded reinforced concrete beam. This work lays the foundation for evaluating the residual bending strength of corroded reinforced concrete beams using the SMFL signal; the micromagnetic sensor is further applied to the civil engineering.

Ultrahigh-performance fiber-reinforced concrete (UHPFRC) is an innovative material in the field of bridge engineering. With superior mechanical characteristics, this new material reduced the structural self-weight and extended the span of modern bridges. A series of tests should be conducted to establish reliable design rules for UHPFRC structures. This paper aimed at determining the compressive behavior of UHPFRC for thin-walled arch section design and a comparison was made with a normal concrete (NC) arch. Eighteen axial compression columns for arch section design and arches under asymmetric load were tested in this paper. Behaviors of the arches were assessed using various mechanical properties, including the failure pattern, load-deflection relationship, strain analysis, and analytical investigation. A finite element model (FEM) considering the material and geometric nonlinearity was developed to predict the behavior of the UHPFRC arch. Results indicated that a wall thickness of 50 mm with stirrups effectively restrained instability failure of the thin-walled compression columns. The cracking load and the ultimate load of the UHPFRC arch increased by 60% and 34%, respectively, when comparing with the NC arch. It showed the UHPFRC arch had higher load capacity and outstanding durability. The failure mode of the UHPFRC arch was similar to that of the NC arch, which belonging to the destruction of multihinges. However, the appearance of the plastic hinges was delayed, and a better elastic-plastic performance was obtained when using UHPFRC. The analytical formula for calculating the ultimate load of the UHPFRC arch was derived with high precision by using the limit equilibrium method. The results of the FEM showed good agreement with test results, and they were able to predict the behavior of the UHPFRC arches.

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