Techniques for buckling experiments on steel silo transition junctions

Large elevated steel silos generally consist of a cylindrical vessel, a conical discharge hopper and a skirt which may either be supported on the ground or by a number of columns. The cone–cylinder–skirt junction is subject to a large circumferential compressive force due to the radial component of the meridional tension in the hopper, so either a ring is provided or the shell walls are locally thickened to strengthen the junction. Many theoretical studies have examined the buckling and collapse strengths of these junctions, but no previous experimental study has been reported. This has been due to the great difficulties associated with testing these thin-shell junctions at model scale. This paper first describes the development of an experimental facility for testing model steel silo transition junctions. Issues covered include the fabrication of quality model junctions using thin steel sheets, the loading method and the precise three-dimensional measurement of geometric imperfections and deformed shapes using a laser-displacement meter. Typical experimental results of a cone–cylinder–skirt–ring junction are next presented to demonstrate the capability of the developed facility. Procedures for processing the test results to determine both the buckling load and the number of buckling waves are also presented.