Tapered Beam stability check - Structural & Architectural Design

RE: Tapered Beam stability check

Shiling Pei — Sun, 09 Mar 2025 02:26:22 +0000

Thanks @heblomgren

While it is not the official recommendation blessed by AWC, I think this is a rational approach. It is good to see American Institute of Timber Construction Manual has a dedicated chapter for tapered beam.

In Eurocode 1995 the tapered beam has a dedicated section (6.4) to consider modification to the "allowable" stress due to taper. But the stability check is in a separate section (6.3) and there is no explicit instruction of how to consider taper in 6.3...

I think this is something that may require more research. But it is a problem probably not significant enough to raise funding to do it.... Maybe I can write a paper on it when I have free time. In practice I will always go with largest depth for stability check if I am to stamp the design 😉

RE: Tapered Beam stability check

HEBlomgren — Sun, 09 Mar 2025 01:27:33 +0000

@ling - Hi. An answer I found comes from the AITC Manual Chapter 7 on Tapered Beam Design - See attached screen snap. Don't forget the Ci and Cvr factor that apply to tapered members and that the taper should be on the compression side. Also - tapered beam have a very important specification regarding the lamination layup and the design strength. This is specified in ANSI 117. 2nd screen snap is the explanation of this in AITC Manual. Lastly - this is a good AWC reference on stability design of beams. It does not look to include any discussion on tapered beams. https://awc.org/wp-content/uploads/2021/12/AWC-TR14-0312.pdf

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Tapered Beam stability check

Shiling Pei — Sat, 22 Feb 2025 17:30:54 +0000

Is there any explicit recommendation in NDS on stability factor CL calculation for Tapered beams?

say I have a beam start from 20" on one end and go to 10" on the other end, what depth should I use to go into the CL calculation?

Using 20 is apparently conservative and OK, but is there any explicit rule for that?

@billkirkham @heblomgren @johnlawson