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The orthotropic plate with the effect of transverse shear is the default option for the calculations. This is an analogy to short, high, etc. beams in which it is not possible to neglect the effect of shear forces T on the deformation, as that effect is comparable to the effect of moments M. This influences the shape of deflection line w(x) and thus also the values of all statically determined quantities, e.g. hogging moments that are decisive for the design.
Practically it means that shear stiffness expressed by shear parameters (shear moduli G13, G23) is taken into account. By default, one material can be used for type STANDART which means that G13= G23= G.
Parameters G13 and G23 are necessary because the Mindlin plate element with a substantial influence of shear forces qx and qy on the deformations is used.
For plates with the dimensions in the range of L / 5 < h < L the formulas for D44 and D55 printed below are used.
In many cases there are no simple formulas to calculate these stiffnesses. The shear force deformation is neglected (as by other FEM elements) when large values are entered for these two constants.
Recommendation:
For plates approximately within the range of:
|wm | ≤ L / 100
h ≤ L / 5
parameters D44 and D55 should be used with large values
where:
|wm | the maximal plate deflection,
h the plate thickness,
L the characteristic plate plan-view dimension,
L the diameter of a circular plate or the shorter side of a rectangular or rhomboid plate, etc.
= 
/ 1,2
/ 1,2 (1)
= 
(2)