Different with definition of continuum mechanics used for beam element, in-plane drilling degrees of shell element are usually based on Allman mode or additional rigid rotation of element sides, and assumption of plane section for beam element is another inconsistency with shell element, at last, the beam section may cover more than one node of shell element with mesh refinement. Therefore, direct connection for these two degrees of freedom may be inappropriate, special connector elements or constraints should be introduced to enforce the stiffness of connection. Numerical results show that the influence of constraints on periods can be neglected, but bending moment at beam end should be simulated with proper additional constraint, compared with the other modes, constraint on drilling degrees of freedom is much more effective.
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