Orthotropic slab implementation
The following properties are required when specifying an orthotropic slab:
-
Ex - Young's modulus in the local X direction
-
Ey - Young's modulus in the local Y direction
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Gxy - Shear modulus in the local XY plane (in-plane)
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Gxz - Shear modulus in the local XZ plane (out-of-plane)
-
Gyz - Shear modulus in the local YZ plane (out-of-plane)
-
𝜈x - Poisson’s ratio in the local X direction
-
𝜈y - Poisson’s ratio in the local Y direction
Note: No distinction is made between
Gxz and Gyz out-of-plane shear moduli.
Using the ‘Calculate properties’ functionality
The material properties are determined based on the X and Y stiffness modification factors, denoted as 𝛼x and 𝛼y, respectively. The factors are applied to Young’s modulus, Edb, and Poisson’s ratio, 𝜈db, defined in the materials database. The shear modulus defined in the materials database, Gdb, is ignored, as the in-plane and out-of-plane shear moduli are derived using the formulae shown below.
Young’s moduli in local X and Y directions
Poisson’s ratios in local X and Y directions
where
In-plane shear modulus
The modulus is established using Huber’s formula:
Out-of-plane shear moduli
where
Manually setting material properties
The material properties can be set manually when the ‘Calculate properties’ checkbox is unchecked. The properties take default values based on their state prior to deselecting the checkbox.
The Poisson’s ratio in the local Y
direction is not directly editable, and is calculated automatically based on the
editable parameters using the following formula:
When manually defining properties of an orthotropic slab item, it is recommended to treat the local X direction as representing the minor direction, i.e. characterized by lower stiffness. This allows modifying the corresponding Poisson’s ratio, which is not possible when the local Y direction is chosen as the minor direction. In case the local Y direction of a slab item needs to represent the minor direction, it’s advisable to rotate the item’s LCS, by offsetting the current X direction by 90o in Slab item properties -> General. Please refer to Slab item properties page for more information.