Abstract
Test results are given in the paper for six 0.6 m diameter welded steel cylinders, stiffened by external T-rings, which were subjected to external pressure. The radius-thickness ratio of the cylinders varied from 185 to 300 and the ratio of the length of the central bay of the cylinders to the radius varied from 0.28 to 0.60. In the assessment of the test results, three design codes were employed, viz. BS 5500, DASt 013 and ASME Code Case N-284.
The main aims of the tests were (a) to determine if the external pressure section of BS 5500 was too conservative in the ‘elastic’ range and (b) to ascertain whether the other two codes always gave safe predictions of buckling pressures.
On the basis of the tests discussed herein, it is concluded that, for externally stiffened cylinders, the reduction factor, α, in BS 5500 could be increased from 0.5 to 0.6 in the ‘elastic’ buckling region. Doing this would have commercial benefits but, before it is done, more tests need to be carried out in order to establish the repeatability of the present results. With regard to the DASt 013 code and ASME Code Case N-284, both of them predicted buckling pressures that were too high in several cases. These codes should be amended, particularly for cylinders which have geometric ratios similar to those tested herein. In connection with this point, the authors have been informed recently that DASt 013 will be replaced by DIN 18800, Part 4, some time in 1989. The buckling predictions of this new code, when applied to the six ring-stiffened models discussed herein, appear to be satisfactory.
Some recent German tests on short unstiffened cylinders are also reviewed and discussed from the viewpoints of the BS 5500, DASt 013 and ASME N-284 codes.
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