risa3d model issues

[JStructsteel]

Im doing some practice modeling a framed building in Risa. For now, I have moment frames each direction. When I just run the self weight model, it gives me wacky results. Im using pin pin at the base.

How do I get "Releases" so I dont end up with the phantom results, and suggestions?

 

[CDLD]

I don’t use Risa, but it looks like you have two different unattached nodes in the top left corner. If you zoom in you can see 2 nodes there.

 

[JStructsteel]

Perfect, thanks. Ive been fussing with it for hours and didnt see that.

 

[Aesur]

@JStructsteel I recommend always using model merge in RISA, often times this can find these kinds of mistakes in modeling. I once saw a model where an engineer was copying nodes a lot to draw plates, ended up having over 5000 extra duplicate nodes in the model and was taking 30+ minutes to run, model merged and took less than a minute to run. It's a great tool!

I think you are definitely on the right track for learning RISA as running with dead load only to see if the shape makes sense is a great practice I wish more people would think of. A few other pointers are making sure you have K factors and unbraced lengths set properly. Also making sure you select the code that matches your load combinations, ie ASD for ASD combinations. These are typically the first things I check in any model done by an engineer and 90% of the time I find one of those items, if not a few or all are wrong.

 

[JStructsteel]

Thanks. The K factor is a good point.

I didnt realize there was a model merge too. This is the first 3D type structure I am doing. Probably would have saved me hours. I need glasses.

 

[EngDM]

@JStructsteel I recommend always using model merge in RISA, often times this can find these kinds of mistakes in modeling. I once saw a model where an engineer was copying nodes a lot to draw plates, ended up having over 5000 extra duplicate nodes in the model and was taking 30+ minutes to run, model merged and took less than a minute to run. It's a great tool!

I think you are definitely on the right track for learning RISA as running with dead load only to see if the shape makes sense is a great practice I wish more people would think of. A few other pointers are making sure you have K factors and unbraced lengths set properly. Also making sure you select the code that matches your load combinations, ie ASD for ASD combinations. These are typically the first things I check in any model done by an engineer and 90% of the time I find one of those items, if not a few or all are wrong.

I had one where I replicated a member radially, and miss counted so the last replication was an overlap, took me way too long to figure out why the joint reaction table was showing double the load of everywhere else.

+1 for model merging.

 

[EngDM]

Thanks. The K factor is a good point.

I didnt realize there was a model merge too. This is the first 3D type structure I am doing. Probably would have saved me hours. I need glasses.

If you are ever doing free-standing structures where K = 2, RISA won't automatically do this (at least in the older perpetual version we have).

 

[JoshPlumSE]

I didnt realize there was a model merge too. This is the first 3D type structure I am doing. Probably would have saved me hours. I need glasses.

Sadly, this is a very common occurrence for me these days. Part of it is the natural tendency for our eyes to see only what we EXPECT to see. The other (at least for me) is the effects of getting older.