Test study on residual stress distribution of hybrid steel u-rib stiffened plates

Orthotropic steel bridges were found to experience early fatigue failures of several welded connections in the steel deck plate. The welding process inevitably produces welding residual stresses and deformations that should be evaluated and considered to better understand the fatigue life of steel bridges. Aiming to study the residual stress distribution of hybrid steel u-rib stiffened plates, the blind hole method was applied. Various parameters, including the plate widths, the ratio of the u-rib thickness to the motherboard thickness, and the steel strength of the combination of the u-rib with the motherboard, were considered, and nine specimens were subjected to experimental tests. The results indicate that strain release factors have great impact on the calculated residual stress: as the value of strain release factor increases, the calculated residual stress in absolute term increases accordingly. However, due to experimental errors, as the ratio of the motherboard to the u-rib thickness varies from 1:2 to 1:2.5 and the u-rib spacing increases from 120 mm to 160 mm, the residual stress value and the distribution change are not obvious; when different steel strengths were used in the specimens, as the material yield strength of the motherboard (u-rib) increases, the residual tensile stress peaks of the motherboard (u-rib) increase, while the residual tensile stress distribution of the u-rib (motherboard) remains essentially the same. Based on the comparison between the cutting method and the blind hole method, the values from residual stress test points appear to be similar; from the perspective of measuring points' distribution and the directions of the tested residual stress, the cutting method cannot test the weld location, and the residual stress at the measuring point can only be obtained along the cutting direction because the blind hole method can test the weld location residual stress, and the residual stress of the measuring point can be obtained in any direction.