Mixed shell element for seven-parameter formulation

A new mixed shell element is developed for a seven-parameter formulation in this paper. The mixed shell element is constructed by assuming stress field and displacement field together. Assumed stress field and assumed displacement field can be combined by stress–strain relationship with Hu-Washizu functional. The developed mixed shell element can provide more flexible stiffness than other commercial softwares. Additionally, seven-parameter shell formulation is used instead of Reissner/Mindlin formulation, since it can provide the thickness change. Even though some commercial engineering software are not proper for very thick shell structure, the developed mixed shell element for sevenparameter formulation can be used without distinction of thick shell and thin shell. An example of shell models with different thickness is provided with solid model. Static and modal analyses are also performed for verification