Truss Design Question
Truss Design Question
(OP)
I am currently working on the design on a cantilevered truss for an outdoor canopy. All members of the truss are to be the same size and based on my loading I have determined that the bottom chord is going to be the critical member in compression. Is there a good reference out there to help me determine the effective length I should be using to size the member? Right now I am looking at the bottom chord as a cantilever and therefore getting a K = 2. This is resulting in a very high KL, which is marking me select a member with a large r to get KL/r <= 200. This approach seams to be too conservative but I can't find any guidance to tell me I can assume otherwise.
Also, as of now - there is no bracing out of plane for the bottom chord, the architect wants to minimize the amount of steel seen.
Any help you guys can provide me would be appreciated.
Thanks.
Also, as of now - there is no bracing out of plane for the bottom chord, the architect wants to minimize the amount of steel seen.
Any help you guys can provide me would be appreciated.
Thanks.





RE: Truss Design Question
RE: Truss Design Question
RE: Truss Design Question
Just to check on my thought process...since I have no bracing in the bottom chord and the truss is cantilevered - my KL will be twice the length of the length of the bottom chord I am considering. I am looking at the bottom chord somewhat in "sections"...for example, my largest loaded member I have a smaller KL since this largest compression force only occurs in the final member in the bottom chord. And my smallest compression force has the largest KL, since when that load is on the farthest member in the bottom chord - that bottom chord could buckle all along the length - in theory.
Like I said - I want to thank you again for your responses...this is the first time I have tried to design a truss and I feel that my thought process is correct, but always feel better to hear others opinion of something.
RE: Truss Design Question
Regards,
John Audu
Nigeria