Fabrication of small models of large cylinders with extensive welding for buckling experiments

Cylindrical shells in large steel silos and tanks are commonly constructed from a large number of curved panels joined by many circumferential and meridional welds (referred to as the panel method hereafter). The extensive use of welding in these shells is a unique feature not previously studied in laboratory buckling experiments due to the great difficulty in fabricating realistic small-scale model shells. This paper presents an innovative technique for the fabrication of small models of such large steel cylindrical shells constructed from many welded panels. The experimental set-ups to implement this technique in the laboratory are also described. The new technique consists of two stages: (a) production of a high quality model by rolling two sheets (or a single sheet) and welding along the meridional seams; and (b) 'welding' in the form of controlled heat input in a required pattern of circumferential and meridional 'welds' on the central portion of the shell surface. The imperfections in an example specimen are also examined to show that they have a realistic pattern. The observed buckling behavior of this specimen is presented and discussed. The specimen buckled at a very low load, confirming that the welding-induced imperfections in such shells are severely detrimental to the buckling strength.