Solid-shell elements form a class of fi nite element models intermediate between thin shell and conven-

tional solid elements. They have the same node and freedomconfi guration of solid elements but account

for shell-like behavior in the thickness direction. They are useful for modeling shell-like portions of a

3D structure without the need to connect solid element nodes to shell nodes. See Figure 1(a).

This report presents in detail the derivation and computer implementation of an 8-node solid shell element

called SS8. Most of the derivation follows the Assumed Natural Strain (ANS) method introduced by

Park and Stanley [21] for doubly curved thin-shell elements and by Bathe and Dvorkin [2] forMindlin-

Reissner plates.