Cylinders with a steel-concrete-steel wall to resist external pressure

In the 1980’s Manchester University carried out over 110 tests on cylinders with a composite wall (steel-concrete-steel) subjected to external pressure as already reported in the literature.  This paper describes further tests on 9 cylinders with a composite wall and a dome end subjected to external pressure and reports the results and compares them with theory.  The cylinders were 500 mm diameter and 1250 mm long and four of them had penetrations through the cylinder wall.  These tests were carried out under contract for Tecnomare SpA of Italy and have not been previously reported because of confidentiality reasons.  The agreement between test behaviour, failure load and the theory developed at Manchester University is good. The philosophy for the design of such vessels for seabed structures is discussed and a ‘depth margin’ method proposed as it is a more realistic way of applying safety.  Examples of designs for different depths are given and compared with the predicted failure pressure.