#### Topic: Floor diaphragm

Hi
I'm using Atena 3D static for my analytic study
my topic is slab action on the building.
For this purpose, I want to compare the behavior of the building with or without floor slab.
To do this, first I conducted the building with floor slab. and I modeled the slab by using the solid element.
And now, I try to model the building without floor slab. and instead of floor slab, I want to impose the rigid diaphragm for each floor.
However, I cannot find the proper way to do this.
Could you have any good suggestion for me
Thanks!

#### Re: Floor diaphragm

Actually, it's quite simple just to define a very rigid elastic material to your slabs (define smth like 1000x stiffer than steel). But is it really needed for your case. Below you can find my ideas about that.

Are you intended to consider nonlinear behavior of materials? I don't think it is really needed for a general case. Maybe you need to perform some linear simulations firstly. Rigid diaphragm is an approximation which is usually applied in linear analysis rather than in nonlinear. Hence, I have some advises to you:
1. Prepare a program of numerical simulations with final goals descriptions and subdivide them into tasks
2. I assume that you find in your program than you need to perform series of linear tests. For this purpose you may use ATENA but it's much easier to use SAP2000/ETABS/Sofistik/Robot/RFEM etc.
3. Some local tasks can be performed in ATENA in order to get correct approximation of a linear model or maybe to check previous assumptions (axial and flexural stiffness of slab or joints etc).

#### Re: Floor diaphragm

Dear zkdhtmzla and Pavlo: just to precise a bit - we recommend to represent "rigid" parts with E 2-20x higher than steel (see also ATENA Troubleshooting, 2.2.19.1 Recommended alternative: Point load and an elastic loading plate). This range usually offers a good compromise between unwanted deformations of the "rigid" part and numerical problems due to extreme stiffness differences (poor conditioning of the equation system).

Regards.