Surface Morphology and Remaining Geometric Parameters of Corroded Members on Bailey Truss

Bailey truss has been widely used in temporary constructional structures of bridges and is reusable. In the service duration, the Bailey truss is commonly exposed to corrosion threats due to the failure of anticorrosion coatings, resulting in corrosion damage on members which induces degradation of its structural behavior. This paper presents an investigation on the corrosion damage of a Bailey truss that had been in service for 8 y in Northeast China. A total of 18 member segments were obtained from the chords, diagonals, and verticals of the Bailey truss, and were scanned by a three-dimensional (3D) laser scanner after clearing the paint and rust. Then reverse modeling was performed based on the 3D coordinates of the specimen surfaces. The surface topography was discussed for different members based on the separated roughness component, the residual thickness was analyzed for plates, and the residual cross-sectional area and moment of inertia about axes of the members were calculated and discussed. Coupon tests were performed on corroded specimens from chords, diagonals, and verticals to quantitatively analyze the degradation of corroded Bailey truss. It was found that the corrosion damage on flanges was more severe than that on webs, in terms of surface roughness and thickness loss. The corrosion status can be influenced by the microstructures and serving location. Upon the true values of the remaining cross sections, it was concluded that the chords, diagonals, and verticals of the Bailey truss all exhibited the largest loss ratio in the moment of inertia about y-axis and the smallest loss ratio in the cross-sectional area. The vertical member had the largest dispersion of average nominal loss rates, especially for the moment of inertia about y-axis, whose maximum and minimum values differed by 157.1%. A practical method for estimating the residual cross-sectional area and moment of inertia was validated. In addition, the engineering mechanical parameters (the elastic modulus, yield strength, ultimate strength, and the elongation after fracture) of each member show linear degradation. The mechanical parameters of the diagonal web are most affected by corrosion. There is 10% thickness loss in the chord web with up to 27% loss bearing capability in 8 y, and the factor of safety with respect to a reference parameter is lowered.