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AS1684.2 mentions that strutting beams may be chamfered to a min of 100mm or 1/3 of their depth (whichever is greater). What are the design rules and methods for checking the minimum chamfer of other beams not obtained from the AS1684 tables. App E of AS1720.1 discusses notched beams, but I am specifically wondering about beams chamfered to fit under a sloping roof. Is it simply a case of checking the shear capacity of the reduced section at the face of the support? Can the App E method be applied to this case?

Woodsolutions Answer +

The limits set out in AS1684.2 apply to solid beams in general, including LVL. For example, Carter Holt Harvey’s literature specifies that chamfer cuts in their Hyspan product must not be less than 17.5 degrees or 1:3, with the remaining section not less than D/3 or 100 mm. Presumably other producers have the same requirement, although you may wish to check if you have a specific product in mind. Chamfer cuts to I-beams are as shown in Appendix J of AS 1684.2.

Question

I am having trouble selecting equivalent strength rated GL beams and posts in lieu of F17 hardwood?

Woodsolutions Answer +

GL beams and posts produced to AS/NZS 1328 have a grade number that indicates their bending stiffness (modulus of elasticity), eg. GL8 grade has a stiffness (MOE) of 8GPa. If you have a design that calls for F17 timber you will need a GL grade with comparable stiffness properties. F17 timber has a characteristic stiffness value of 14GPa. There is no GL14 grade so you would need to go to the next higher grade which is GL17. Note that imported glulam may be graded differently, as explained on our website here: https://www.woodsolutions.com.au/blog/aus-vs-imported-glulam-markinglabelling.

Question

Are blackbutt posts suitable for a rammed earth footing? Previously I have used ironbark for the horse shelter frames, but supply is a problem. Blackbutt has been suggested as an alternative. 6 lengths cut three sides 3.6 m long. 

Woodsolutions Answer +

Blackbutt is rated Durability Class 2 in the ground according to Australian Standard 5604. This indicates a probable life expectancy of 15 to 25 years. If you are in a dry part of the country and the ground adjacent to the posts is not likely to be damp for long periods, and you can organize some termite protection, this estimate might be significantly exceeded. However, ironbark is rated Durability Class 1 so is a more durable species. There are not many Class 1 timbers that are readily available – other Class 1 options include tallowwood and some of the ‘box’ species (grey box, red box, white box, yellow box). You will find more details about timber properties on our website here: https://www.woodsolutions.com.au/wood-species

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