8 Nodes Or 9

The chief advantage claimed for nine-noded shell elements is that they can pass constant curvature patch tests with bilinear element geometry while eight-noded shell elements cannot. It is shown that a simple modification of the shape functions of an eight-noded element can make this advantage disappear. Test results confirm this result and show that the performance of a modified eight-noded element is similar to that of recently reported nine-noded elements.