Wind Loads in RISA3D and RISA Foundation

[bootlegend]

Anyone care to describe how they handle wind load combinations when using RISA3D and RISA Foundation? Specifically, do you use two separate basic load cases for the two different roof pressure values? Seems like the only way to keep the roof wind load separate so that it can be added to load combos without doubling them.

 

[TehMightyEngineer]

Yes. I also often make much simpler models where I remove a lot of individual members to get towards a more simpler model. Much easier to verify that forces are being transferred properly that way. Often times I'll even create models that have only just a line of shearwalls and input loads manually if I'm questioning RISAs load path.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[bootlegend]

@TehMightyEngineer,

Thanks. My structure is pretty simple in this instance. It does have a monoslope roof so I end up with several possible pressures on the roof. Previously I've just set up a basic load case in RISA3D for each wind direction with the heavy and light roof load. I end up with +X(heavy) and +X(light) as two separate load cases. Works okay in RISA and I just copy the one case over and change the load on the roof members. The trouble I was having was linking the 3D model to RISA Foundation. The load combos in Foundation are based on load categories. The two basic load cases I mentioned in RISA would both be assigned the WL+X load category. So when setting up a load combo in Foundation with the WL+X category I would be doubling wind loads.

The way I decided to handle it is just use a basic load case in RISA for wind load on walls and combine with all of the possible roof wind load cases. I just have to use the generic OL load category for each roof wind load because there is no roof load category in RISA. But, it works and I can link the two programs without too much trouble.

 

[azcats]

I had a similar issue a couple weeks ago going from tnxTower to RISA FDN. How I worked it out is here: [URL unfurl="true"]https://www.eng-tips.com/viewthread.cfm?qid=453640[/url]