Semi-Rigid Diaphragm (Elastic Diaphragm) Behavior
It is the analysis of slabs by dividing them into shell elements and taking into account their deformations.
With Semi-Rigid Diaphragm Behavior;
Slabs are divided into shell elements.
Since the in-plane effects of the slab are taken into account, it gives more precise results.
Story masses are considered as distributed masses along the slabs.
Preferred building types;
Structures with plan irregularity and torsional irregularity
Structures with slab discontinuity
Structures with beamless slab system
Structures with rib or cassette slab system
![](../__attachments/2239955034/image-20221026-140647.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
![](../__attachments/2239955034/image-20220602-143042.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
The slab is divided into shell elements and deformations are taken into account.
![](../__attachments/2239955034/image-20221026-143026.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
![](../__attachments/2239955034/image-20220603-060600.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
When we compare the rigid diaphragm and semi-rigid diaphragm models, different displacement values are seen in the middle region of the models.
In the semi-rigid diaphragm model, the displacement value is 0.163 millimeters.
![](../__attachments/2239955034/image-20220603-063217.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
![](../__attachments/2239955034/image-20220603-063328.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Taken from ideCAD Finite Element Guidelines from pages 57 to after.
Diaphragm Modeling Selection
To model a Semi-Rigid diaphragm, select the diaphragm modeling method from the Analysis Settings dialog.
![image-20240305-124458.png](../__attachments/2239955034/image-20240305-124458.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Display of Horizontal Loads
![](../__attachments/2239955034/image-20220603-063623.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Behavior of Structure Under Vertical Loads
![](../__attachments/2239955034/image-20220603-071208.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Examination of Transitional Storey Structures with Semi-Rigid Diaphragm
![](../__attachments/2239955034/image-20220603-073819.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Examination of Structures with A2 - A3 Irregularity with Semi-Rigid Diaphragm
![](../__attachments/2239955034/image-20220603-073803.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
Examination of Structures with Beamless Flooring with Semi-Rigid Diaphragm
![](../__attachments/2239955034/image-20220603-073750.png?inst-v=e297b259-93ee-4526-bee7-06170d782e4d)
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