If the wrinkling occurs only in the single stress direction of some element, this element remains in forces.So the cable slacking element and the membrane wrinkling element are presented.

• 薄膜结构如果在某膜单元的单向应力方向发生皱折，其单元本身仍然能够继续承受荷载，因此提出索松弛单元和膜皱折单元处理薄膜的索松弛和膜皱折问题。