Lateral Stability model basics

[Anonymous]

Hi,

I have calculated by-hand the lateral stability of an RC building with shear walls (fairly simple arrangement) by the traditional method of rigid diaphragm taking account of individual wall stiffnesses and location of shear centre.

I wanted to verify this in Robot and get a better idea about the drift. Is there a posted example of how to do this which starts at the very basics? I've attached a fictitious example model in which I've tried to ensure I get the modelling basics correct before applying to my real example.

Do you need columns if you're purely checking a lateral case?

Do you assign the slab as rigid diaphragm and walls as a shell?

Spring or Rigid supports at base of wall?

One of the models I created had a reaction corresponding to the direction of the wall weak axis. What's the best way to avoid this?

In the model attached, surely there is single reaction at the top of each wall resulting in an equal magnitude but opposite direction force (MY/I). You'll see 1 wall has different magnitude reactions at each end of wall (a load case with purely wind and no gravity loads)?

PS tried uploading model but I was getting an error message about file type. If you help with this as well it would be much appreciated.

Thanks in advance.

[saclovitzky]

Hello,

Just model the building similar what you did in your hand calculations.

1. Make your model as simple as possible, model the lateral resisting elements such as columns/walls/slabs.

2. Depend on your code you are using, use "stiffness modifiers" for moment redistribution and cracked properties(concrete).

3. check your load combinations(varies with code).

4. use rigid or semi-rigid diaphgram for your slab(semi-rigid recommended)

5. model walls as shell elements, etc.

6. Before running your model, you must, at least, have an idea of the sizes of your structural elements.

7. If your new in using ARSAP there's a lot of videos in youtube , I would suggest to have a quick look on them ,they are  effective tools  in learning the software.

These are only a couple of suggestions and hoping this will guide you in the right direction.