Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: RISA, Lb-comp top and bottom

[Subject Prev][Subject Next][Thread Prev][Thread Next]
From what you are saying it sounds like Lb-comp-top = 4'-0".  The top flange is supported only. When you put the beam in with the global Y upwards, it is having the positive local y upwards and this is considered the top of the beam.  If you had the beam rotated around it's x-axis 180 degrees then you would use Lb-comp-bottom = 4'-0".  If you drew the frame upside down in RISA and had your loads going upwards then you would have use Lb-comp-bottom = 4'-0".

From: john smith [mailto:steelstudent(--nospam--at)]
Sent: Thursday, February 16, 2006 7:55 AM
To: seaint(--nospam--at)
Subject: RISA, Lb-comp top and bottom

Hi all, i'm new to the listserve and am currently and engineering student.

I started playing around w/ RISA and have a few question regarding Lb-comp.

I know Lb-comp is the unbraced length of the compression flange, but i'm cofused about the top and bottom part.

If i have simply supported beam w/ steel roof joists bearing on top of it at 4'-0" o.c., is Lb-comp-top = Lb-comp-bottom = 4'-0"?