Hi,

the rershell element is basically superposition of two elements:  cct plate element, which describes the bending part and trplainstress element describing membrane action. For plain geometry the bending and membrane behavior is uncoupled, so one can simply combine both elements. The cct (constant curvature triangle) is described in the book of  Bittnar and Sejnoha (as mentioned in Mikael reply to your post concerning cct element) and constant strain element for membrane action could be found elsewhere.

Borek