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Question

I am looking at designing a covered outdoor area using timber. I assume LVL is the correct product to span circa 20m.
The timber is external but undercover. It will not be exposed to the rain.
My client wants minimal maintentance.
What treatment is appropriate to the LVL and how long until first maintenance?

Woodsolutions Answer +

For a 20m span some kind of ‘engineered’ product would be needed since sawn timber is not available in such long lengths. Of course shorter spans could be supported with posts. For a clear span, LVL will be fine although for a higher quality appearance you could consider glued laminated timber (‘glulam’). LVL is produced with a structural grade face and is not generally used in appearance applications unless a rustic look is desired. While a 20m beam is theoretically possible to produce, it’s beyond the usual range of sizes used in domestic construction and likely to require a special order. We suggest you discuss lead times and transport considerations with an LVL producer. If the timber is shielded so it won’t get wet when it rains, preservative treatment is not necessary and the usual range of paints and exterior wood stains can be used. Maintenance will not be an issue if the timber is not exposed to the weather.

Question

I am trying to find a design guide or manual for the design and specification of nail laminated timber including:
- reduction factors relating to lamination
- maximum spacing of nails etc.
Do you have any resources that focus on nail lamination?

Do you know of any guides for horizontal lamination for example where the plane of lamination is parallel to the axis of the moment where there maybe shear in the plane/

Woodsolutions Answer +

Vertical lamination:

If you have access to Australian Standards nail lamination is covered in Section 2.4.5 of AS 1720.1, Timber structures, Part 1: Design Methods. Section 2.4.5 is titled Strength sharing between parallel members. The calculation of the modification factor for strength sharing, k9, is given as equation 2.4.5.3. For nail-laminated members AS 1684.2 Residential timber-framed constructionassumes nmem = 1.0 and ncom = number of combined sections in calculating k9. Or to keep it simple just refer to AS 1684.2, Section 2.3 where the recommended nail pattern is shown.

Horizontal lamination:

It is surprising how few resources there are for designing horizontally laminated timber. We haven’t been able to find any guides or tables so designs would have to be calculated from first principles according to the shear capacity of the fasteners (nails, screws or bolts). There is an example calculation here, but since it’s a US site all values are in imperial units: http://hyperion.usc.edu/courses/ame204/Homeworks/HW6.pdf.

Question

I am trying to find a design guide or manual for the design and specification of nail laminated timber including:
- reduction factors relating to lamination
- maximum spacing of nails etc.
Do you have any resources that focus on nail lamination?

Woodsolutions Answer +

If you have access to Australian Standards nail lamination is covered in Section 2.4.5 of AS 1720.1, Timber structures, Part 1: Design Methods. Section 2.4.5 is titled Strength sharing between parallel members. The calculation of the modification factor for strength sharing, k9, is given as equation 2.4.5.3. For nail-laminated members AS 1684.2 Residential timber-framed construction assumes nmem = 1.0 and ncom = number of combined sections in calculating k9. Or to keep it simple just refer to AS 1684.2, Section 2.3 where the recommended nail pattern is shown.

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