ELSEVIF!R Thin- Walled Structures 22 (1995)217-239 © 1995ElsevierScience Limited Printed in Great Britain. All rightsreserved 0263-8231/95/$9.50 0263-8231 (94)00032-8 Elastic-Plastic Analysis of Internally Pressurized Torispherical Shells J. Sori6 a & W. Zahlten b Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Dure Salaja 5, 41000 Zagreb, Croatia hinstitute of Statics and Dynamics, Ruhr University Bochum, Universitaetsstrasse 150, D-4630 Bochum 1, Germany (Received 7 July 1993; accepted 23 May 1994) ABSTRACT The constitutive equation for an.elastic-plastic material model was derived ush~g the yon Mises yield criterion and assuming isotropic strain hardening. A layeredfinite element permitting geometrically linear and geometrically nonlinear elastic-plastic analysis of thin shell structures is presented. The effect of linear strain hardening on the size of plastic regions and the dis~,ribution of internal forces in an internally pressurized torispherical shell was analyzed. At sufficiently high pressures a significant difference in the dis~!ribution of internal forces was observed between elastic, perfectly plas- tic .and strain hardening material. The effect of the size of plastic regions on the difference in the magnitude of internal forces obtained by geometrically linear and geometrically nonlinear computations of the torispherical shell was studied. An increase in the size of the plastic region was found to produce greater differences in the computation of meridional bending moments than in the computation of hoop stress resultants. INTRODUCTION Torispherical shells are frequently used as end closures on pressure vessels and different types of cylindrical containers which can be found in various fields, such as aerospace, food processing, chemical, nuclear and oil industries. The investigation of internally pressurized torispherical shells was prompted by the failure of a large fluid coker undergoing a hydro- 217