A DISPLACEMENT-BASED GEOMETRICALLY NONLINEAR CONSTANT STRESS ELEMENT

A triangular geometrically non-linear constant stress element is presented, applicable to thin-shell problems involving finite rotations. The element has the same degrees of freedom as the linear element following from the superposition of the constant strain triangle and the constant moment triangle. In the derivation of the non-linear strain-displacement relations, special attention is given to the correct representation of the rigid body motions of a patch of elements. Based on a second-order out-of-plane displacement field, an initial deflection is introduced. This improves the effectiveness of the element, since curved shell geometries can be described more accurately. Several demonstrative examples are included.