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Re: Torsion in Wood Members

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What if the depth is the smaller side dimension?

On 2/7/07, AWC Info <AWCInfo(--nospam--at)> wrote:

AF&PA/ASCE 16-95 Standard for Load and Resistance Factor
Design (LRFD) for Engineered Wood Construction
Section 5.5:

5.5 Resistance of Members in Torsion

The adjusted torsion resistance, Mt', of a solid
rectangular beam shall be computed as:

Mt' = (b^2 d^2 Ftv')/(3d + 1.8b)

where b is section width, the smaller side dimension;
d is section depth, the larger side dimension;
and Ftv' is adjusted torsional shear strength.

For section shapes other than rectangular, the
ajusted member torsion resistance shall be based on
linear elastic torsion analysis with Ftv' used as the
maximum torsional shearing strength.

For solid sawn lumber, Ftv' shall be taken as
two-thirds of the adjusted horizontal shear
strength, Fv'. For glued laminated members, Ftv'
shall be limited to Frt', the adjusted radial tension

The torsional resistance of structural composite
lumber members is not within the scope of this
standard and requires special investigation.



John "Buddy" Showalter, P.E.
Director, Technical Media
AF&PA/American Wood Council
1111 19th Street, NW, Suite 800
Washington, DC 20036
P: 202-463-2769
F: 202-463-2791

The American Wood Council (AWC) is the wood products division of the American Forest & Paper Association (AF&PA). AWC develops internationally recognized standards for wood design and construction. Its efforts with building codes and standards, engineering and research, and technology transfer ensure proper application for engineered and traditional wood products.

The guidance provided herein is not a formal interpretation of any AF&PA standard.  Interpretations of AF&PA standards are only available through a formal process outlined in AF&PA's standards development procedures.


From: "John J. Treff" <jjtreff(--nospam--at)>
To: SEAInt < seaint(--nospam--at)>
Subject: Torsion in Wood Members

Hello Colleagues,I've been looking for information about design for torsion= in wood members (timber and glulam). The only decent reference I've found = is the AITC Timber Construction Manual (5th edition). In section 4.3 gives = an excellent approach to design for torsion, but using ASD. I am looking fo= r references with the LRFD approach. Any ideas?JJ