So what degrees of freedom are you wanting to restrain (and which direction is vertical/up in your model)? Have you tried double-clicking the node and changing the boundary conditions to "reaction" where you want restraint, and "free" where you do not want restraint?

I dont understand the issue i guess - a general pin support restrains translation in all directions. If you want a certain direction unrestrained, you can modify that too, achieving whatever restrain you want. It should appear graphically as well, so you can verify you applied the restrain correctly.

I didn't realize I could edit the restraints. I thought once I hit the support button and hit pin that that was the conditions. I'm very new to RISA as this is my first month on the job as a new EI. But now I see which directions I can restrain and leave free with the pull down menus. Thank guys.

@UcfSE I'm looking to restrain the z direction in my model and y direction is vertical. I'm still kind of confused what reaction means for the boundary condiditon.

The project I'm working on is removing an exchanger unit and to do so two channels are bolting to either side of a square concrete pedestal (flanges out) and I'm trying to figure out how to model that connection correctly.

From the sounds of it the two channels should be fixed at one end, free at the other. The connection would then be designed for the moment and shear output from RISA, and also verified by hand. The pedestal then need to be checked for the added moment.

Do you have a screen cap, or a sketch?

Have you tried RISA's help file? It's generally very useful.

I'm trying to figure out how to correctly model the boundary conditions of the 4 channel beams that are in between the 2 W Beams. It's going to be bolted to a concrete pedestal through the web of the channel and that's it.

• http://imageshack.us/a/img600/9126/dzw.png

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• http://imageshack.us/a/img600/9126/dzw.png

.....

• http://imageshack.us/a/img600/9126/dzw.png"
• alt="Image
• Hosted
• by
• ImageShack.us

I can't figure out how to upload it with imageshack. I thought I was copying and pasting the correct link but I guess not.

...

• http://imageshack.us/a/img600/9126/dzw.png

There we go...^^^^^^ that one works.

If it is truly a pinned support that means it would have translational support in all three directions while being free to rotate. The orientation of a pinned support is meaningless as it has the same resistance in all directions.

Now, I don't fully understand your design condition and what resistance the support piers are going to provide. If it is truly going to restrain translation in all directions and be free to rotate then you would be correct to model it as a pinned support. If not, then you can manipulate the restraint at that joint just by double-clicking it and manually setting the boundary conditions for each degree of freedom directly.

There are ways to provide "rotated" boundary conditions in RISA, but this is more of an advanced modeling feature that is rarely used. It is used exclusively when you have structures that are not aligned with the global axes... like circular tanks or inclined beams with rollers. I don't think that applies at all to your situation, so I don't think we should get into it. Just know that it is possible if you run into the situation at some point in the future.