Strength properties of pinned connections in aluminium truss girders

Pinned element connections in aluminium trusses are investigated experimentally [2]. Forces in the connections are transferred through shear and bearing. Because the inner cylinder and the securing pins are conical, there is no play in the connection when it is assembled. Securing the pins with springs allows for fast assembly and disassembly. In practice also nuts are used for securing the pins. The parameters investigated in the research are the boundary conditions (hinged or fixed in clamps of the test bench) and the way the pins are secured (with springs or with nuts). The mean maximum load at structural failure is 136 kN. This load was not influenced by the parameters investigated. The maximum elongation at structural failure is influenced by the way the pins are secured. The use of nuts (series II) results in more elongation (sample mean 14.7 mm) compared to the use of springs (series I, sample mean 13.1 mm). The load at maximum elastic deformation is influenced by the boundary conditions in the test bench. The clamped specimens show a mean elastic load limit of 39.7 kN, which is approximately 12 kN lower than the hinged specimens which show a mean elastic load limit of 51.4 kN. This can be explained by the additional stresses in the fixed connections resulting from the prevention of rotations, leading to a lower limit for elastic loading. The elastic connection stiffness is dependent on the way the pins are secured. The stiffness using springs is 56.9 kN/mm, which is considerably higher than the stiffness using nuts which is 39.3 kN/mm.