Advances in the Analysis of Prestressed Concrete Pressure Vessels

Abstract The paper describes recent developments in the structural analysis of prestressed concrete pressure vessels with particular reference to work carried out by the Central Electricity Generating Board's Berkeley Nuclear Laboratories. Since the first concrete pressure vessels were designed, considerable advances have been made in the fields of elastic and thermal analysis. The paper shows typical applications of the finite element method to concrete vessels, and discusses the correlation obtained with both site and experimental measurements. Creep in concrete has been shown to be of importance due to the stress reversals which can occur on cooling. Correlations are shown between strain predictions and site measurements over the first five years of the life of the Oldbury vessels. The time increment type of creep analysis is shown to be valuable in the examination of detail problems. For example, the effect of standpipe reinforcement on the creep behaviour of a top cap has been assessed. Such methods are however, expensive in computer time for the examination of a full non symmetrical vessel geometry. The paper shows how viscoelastic collocation, and other techniques can be used to study creep behaviour with a minimum of computation. Finally, some criterion is required for assessment of the multiaxial stress states calculated by these advanced computer methods. A simple graphical method is shown, based on experimental results, which allows the rapid assessment of the acceptability of a multiaxial compressive stress state in concrete.