steel truss/frame

[david_peterson]

I'm working on a project that's going to require the use of a 68' clear span rigid frame truss; much like the style shown in the ADT 2005 (2500+page) user's manual (chapter 27, page 1212). So I went through the example and got poor results. It's going to be a 12/12 pitch using W33's or W36's for the top chords and W21's or W24's for the columns. The problem occurs at the W33 to W21 joint where it should miter the 2 sizes together. But for some reason it didn't complete the miter and taper the W21 past a 45 degree angle.
I've attached the file, if anyone can tell me what I did wrong it would help out a lot.
Thanks

[Steve_Bennett]

I'd like to help, but when I click the picture, there is nothing to view.

[david_peterson]

It's a 2005 format, that may have something to do with. I tried it, opened fine for me. Try a zoom extents.

[Steve_Bennett]

I should have known that Internet explorer can't open ADT files. duh. :screwy:

Anyways, I figured it out! I follwed the example you mentioned to the letter & realized what was happening. When you convert the linework to the truss, it places the beams on a justification of Middle Center along the line that was drawn. Since they wanted a tapered profile to the edge of their truss, ADT knew to miter the corners becuase that was the only way to get a tapered profile.

When I looked at your example, I saw that obviously was not what you wanted. Again, the beams were placed on a Middle Center justification along the path of the line. This made me wonder what would happen if I started to mess with offsets to force the corners to miter. So I started playing around with the X,Y,Z offsets to see what happened. As I messed with different offsets & observed the affect it had on the truss, I began to understand how they worked. The final tweak was to do this: Under Start Shape, for components 2 & 3, I set the Y offset to -6". What this did was drop the height of the two rafters down 6", forcing the corners to miter.

I highly recommend to always mess around with all boxes in a custom structural member when it does not perform the way you expect. Just from doing that & observing the changes, one can learn a great deal.

I posted the file I modified with the final solution in case my jibberish doesn't make sense. I hope this answers your question.

[david_peterson]

Thanks for the help and the suggestion. I'll have to remember that for next. I figured out how to get basically the same thing by using cut planes, and offseting them. Now if I could just figure out how to get it to display correctly.