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Diaphragms

Definition

A diaphragm is a 2D member
A diaphragm has no bending stiffness
A diaphragm has in-plane stiffness, which depends on the type of diaphragm (rigid, semi-rigid or flexible)
The loads applied to a diaphragm are distributed to its underlying beams (or other underlying entities) in the same way as with a load panel
The self-weight of a diaphragm is distributed to its underlying entities, in the same way as other applied loads

At this point, only composite decks and metal decks can be used as diaphragms.

Available types of diaphragm

Rigid diaphragm

The 2D member has no bending stiffness and infinite in-plane stiffness in the analysis model. The loads applied to it, as well as its self-weight, are transmitted to the supporting members in the same way as for a load panel.

Semi-rigid diaphragm

The 2D member has no bending stiffness. Its in-plane stiffness is taken into account in the analysis model by means of a finite element mesh. The loads applied to it, as well as its self-weight, are transmitted to the supporting members in the same way as for a load panel.

Flexible diaphragm

The 2D member has no in-plane shear stiffness nor shear stiffness in the analysis model. The loads applied to it, as well as its self-weight, are transmitted to the supporting members in the same way as for a load panel; in-plane loading is transferred only axially, without transverse diffusion.

How to create a diaphragm

Create a 2D member
Select Element type = Composite deck or Metal deck
Select Element behaviour = Rigid diaphragm or Semi-rigid diaphragm or Flexible diaphragm

Composite deck and Metal deck element types are available only when both concrete and steel material types are enabled in the project settings.

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