Improved Allman-free zero-energy mode planar triangle element

finite elements;  Rotational degrees of freedom;  Zero energy mode;  Triangular elements

Based on the original Allman cell with rotational degrees of freedom, some modifications are made to the original Allman cell functional potential energy II.p from the definition of rotational components, and a new unit is derived. This unit successfully eliminates the main defect of the Allman unit - the redundant zero-energy mode, while maintaining the advantages of the unit: the column formula is concise, the accuracy is high, and the good characteristics of the improved element are confirmed by the given example.