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Question

We design timber members to suit structural loads using AS/NZS1720.1. We have some laminated finger jointed timber of a specific species that we would like to use, and want to get it tested to measure the structural design properties used by AS/NZS1720.1 to determine the design capacities of elements and joints. Could you please advise us of the requirements and regulatory documents (eg. Standards) we must follow to achieve this?

Woodsolutions Answer +

We understand that Dr Constantine ('Con') Adam is the Director of the Glued Laminated Timber Association of Australia (GLTAA) Inspectorate. Dr Adam would be able to advise you on the required test protocols. You will find his contact details via this link https://gltaa.com.au/members/university-of-melbourne.

Glulam accreditation

Answered on 15-04-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

Question

We are proposing to use a CLT/ Glulam structure as a proposed new floor to an existing structure.
As it will be situated within the existing Substation exhaust, we will be requiring to have an FRL of 180/180/180 within 3m of openings.
1. Are there any known/ tested Timber solutions (CLT & Glulam) which achieves FRL 180/180/180?
2. What alternative solutions are there, ie. fire rated cladding etc. We are looking to expose the timber on the soffit but will require this fire rating at a small portion.

Woodsolutions Answer +

An FRL of 180/180/180 refers to the ability to maintain structural adequacy, integrity and insulation when exposed to fire for 180 mins. "Integrity" means the ability to resist the passage of flames and hot gases,  while "insulation" in this context means the ability to maintain a temperature below prescribed limits on the surface not exposed to fire. We are not aware of an intumescent fire retardant coating that will achieve an FRL of 180/180/180, but you could inquire from companies marketing such products. Alternatively, it's possible that a material such as CSR's Hebel Powerpanel would achieve the required FRL, applied to the CLT, and certified by a fire engineer. However, we were not sure whether the FRL was required for the upper surface of the floor or the underside. So we are unable to provide a definite answer to your question, just avenues for further inquiry.

FRL

Answered on 12-04-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

Question

AS1684.3 does not provide any guidance on how to account for the effect on the floor bearers of the eccentricity of lateral wind load on shear walls. Whist guidance is provided to ensure the tie down connectors are sufficient to prevent overturning, there is no discussion about what effect this has on the bearer that the tie-down is secured to. The moment caused by the load eccentricity is resisted by an overturning couple at the ends of the shear wall, which then is resisted by bending in the bearer and a reaction couple at the ends of the bearer. In a cyclonic area this can become a very significant load on the bearer, in some cases more critical than direct wind pressures or vertical gravity loads. Are you able to advise why none of the guidance ever discusses this point? Are there any articles you could direct me to which discuss this?

Woodsolutions Answer +

AS1684.3 (Cyclonic areas) has been engineered to take into account all of the load actions on houses - gravity, live loads and wind loads on members as well as building racking, overturning, sliding (shear) and wind uplift (connection and tie-down) actions. There are many post cyclone surveys undertaken to better understand the performance of timber frames and there have been no specific issues identified when the house has been designed to AS1684.3. A consultant who could provide a more detailed response is Colin MacKenzie in Brisbane, email colin@timberexpert.com.au, website http://www.timberexpert.com.au.

Cyclone design

Answered on 26-03-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

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