A simple flat triangular shell element revisited

The 18 degree-of-freedom flat triangular shell element is reformulated by combining the well-known bending triangle with a plane stress triangle incorporating in-plane rotations at each vertex. Both elements are displacement formulated. The plane stress element's displacement interpolation is incomplete and hence convergence to exact solutions is precluded. Comprehensive test results are presented for several types of problem including plane stress, thin shells and folded plates. The results indicate that the element does produce rapidly convergent answers. However these answers are not the correct ones, although they may be acceptable engineering approximations in many applications. Further, the element seems to provide reasonably good results even for relatively coarse element grids.