A hybrid stress nine-node degenerated shell element for geometric nonlinear analysis

Abstract

A stabilized nine-node degenerated shell element, previously derived for linear analysis by the admissible matrix formulation, is extended to geometrically nonlinear analysis. The assumed stress modes pertinent to stabilization matrix are contravariant in nature and their energy products with the displacement-derived covariant strain can be programmed without resorting to numerical integration and the Gram-Schmidt orthogonalization. Numerical tests show that its accuracy is virtually identical to the uniformly reduced integration element.