Nailed Tubular Connections under Axial Loading

An experimental research program on nailed steel tubular connections is described. The “nailing” of one tube to another coaxial tube within it is achieved by a powder-actuated tool and very high strength driven pins (or nails). Combined steel thicknesses of up to 13 mm (1/2 in.) have been easily connected. Furthermore, these structural connections are made very quickly and safely after minimal training with the equipment. A range of tubes up to 406 mm (16 in.) in diameter, with various diameter-to-thickness ratios, tube wall thickness, and lack of fit, have been joined and 42 tube connections have been tested to failure under axial tension or compression loading. The observed failure modes were nail shear failure, tube bearing failure, and tube shear out failure, for which simple prediction formulas are verified. A recommended load and resistance factor design (or limit states design) procedure for such axially loaded tube-in-tube connections is then advocated.