Strain Distributions in Hemispherical GRP Vessels with Radial Branch Connections Subject to Internal Pressure and Radial Load

Abstract

Experiments were conducted on two glass fibre reinforced plastic (GRP) hemispherical vessels, each of internal diameter 1 m. Each had a radial cylindrical nozzle, of 200 mm inside diameter, of similar construction to the vessel which consisted of layers of ‘E’ glass fibre chopped strand mat with a polyester resin matrix. One vessel was reinforced local to the nozzle, while the other had no such reinforcement. Strain gauges on internal and external surfaces were used to measure strain distributions due to internal pressure loading and separately due to local loads applied along the axis of the nozzle. For those tests strains were restricted to values below 0.2 per cent. The measured strain distributions were compared with strains calculated by the thin shell computer code BOSOR4. Finally, tests to destruction were carried out on both vessels under internal pressure with strains being measured up to the level of reliability of the gauges. The agreement between measured strains and those predicted by the thin shell theory was good, except at the nozzle/sphere junction.