Shear and Flexure interaction in timber members (NZS 3603)

Question

Shear and Flexure interaction in timber members (NZS 3603)

Jack_TECL (Structural)

(OP)

19 Jun 22 23:21

Hi Team,

I am working on a bridge deck problem where the shear capacity of the deck is highly utilized at ULS (~95%) and the flexural capacity utilization is less significant (~65%). In steel analysis, shear/flexure interaction is considered and flexural capacity is reduced if shear demands become significant enough.

I haven't been able to find any mention of shear and flexure interactions in any NZ timber design resources.

Does shear and flexure interaction carry any weight in analysis? i.e if shear is 90%+ utilized, does that reduce the member's flexural strength.

Cheers :)

Agent666 (Structural) · Answer 1 · 2022-06-20 08:29:51

Not that I know of. The reason is the maximum stresses in timber do not coincide, for shear the stress is parabolic for a rectangular member, so zero at the location where flexural stresses are at a maximum at the extreme tension and compression fibres.

In steel if you're dealing with say an I section, the shear stress at the underside of the flanges is still quite high so there is interaction when you also consider typically you're going to have a plastic distribution of flexural stresses for compact sections.

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Jack_TECL (Structural) · Answer 2 · 2022-06-20 21:35:00

Awesome!

Thanks, Agent 666. This was the conclusion I had also derived from my research.

Agent666 (Structural) · Answer 3 · 2022-06-21 06:44:16

The only time you might see some interaction in codes or guides is at notches and penetrations come to think of it. If you don't have that then ignore.

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Shear and Flexure interaction in timber members (NZS 3603)