Experimental study and parametric analysis of the vertical bearing capacity of steel hoops under flood–induced wetting conditions

This study investigates the effects of flood–induced wetting on the vertical bearing capacity of steel hoops confining concrete columns. Experimental and theoretical analyses were conducted, including static and dynamic friction tests between steel plates and concrete surfaces, as well as vertical bearing capacity tests of steel hoops under water–layer conditions. The results indicate the following: (1) The friction coefficient showed minimal dependence on vertical pressure under identical conditions, and the vertical bearing capacity of steel hoops increased with higher preload applied by high–strength bolts. (2) For static friction, the coefficient was lowest under dry conditions, moderate under wet conditions, and highest with a water layer on the concrete surface. For dynamic friction, the coefficient was lowest with a water layer on the concrete surface, moderate under dry conditions, and highest under wet conditions. (3) The contact between the steel hoop and concrete column was non–uniform. Under high–strength bolt preload, close contact occurred primarily in the central region and near the wing plates of the steel hoop. Friction under vertical loading was concentrated in these regions, making them prone to local damage in practical engineering applications. (4) In dry conditions, the vertical bearing capacity calculated using either static or dynamic friction coefficients closely matched the experimental results. However, when a water layer existed between the steel hoop and the concrete column, the calculation results based on the dynamic friction coefficient were consistent with experimental values.