Best Way to Model?? 1

[BadgerPE]

Hey all!

I am evaluating an existing building and am wondering what the best way to model a situation where rafters bear on "beams" and "beams" bear upon "girders". My question is specifically in regards to the different elevations of all of the members. Is it best to model with rigid links, slave joints, or draw all members at the same elevation and perform a model merge?

 

[JoshPlumSE]

Crackerjack -

How you want to model something like this depends on what you're looking for in your analysis results. If the only analysis you're looking for is related to vertical loading then the different elevations should have an insignificant effect. The only load transferring between the members should be vertical shear. So, I'd keep my model as simple as possible (with all beams modeled at the same elevation).

If you believe the different elevations will have a significant effect on the analysis (because the axial load in one member will create a moment or a torque in the connecting member) then you can use the Rigid Link method you described. There is a section in the RISA-3D help file called Modeling Tips - Modeling One Member Over Another. This section describes the procedure in more detail that I can do so on this forum. Personally, I try to avoid this extra modeling whenever possible as I like to keep my models as simple as possible.

 

[msquared48]

The best way to model is on a runway.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BadgerPE]

Thanks Mike!

Now if only the email alert didn't wake me from a dead sleep....lol