FRP for Structural Adequacy for Concrete Walls

[ShawThing]

Hi
My question is in relation to clause 5.7.2 of AS3600 paragraph 2.
Does that mean if you have a steel wall head/wind beam supporting the top of a panel like you might have between steel portal frames (like a PFC on its flat for example) that you can adopt the panel thickness values in table 5.7.1 for structural adequacy as opposed to the values in table 5.7.2?
Regards

 

[rscassar]

You need to use both tables, 5.7.1 is insulation and 5.7.2 is adequacy. Refer to the NCC and it will give you the difference between the two. Thickness will likely be governed by 5.7.2.

 

[ShawThing]

Thanks for your response.
I am trying to work out the panel thickness required for a structural adequacy of 240 mins.
I have seen elsewhere 170 thick is ok for this but 5.7.2 seems to a lot thicker than this.

 

[rscassar]

How recent were the projects u are comparing too? Fire provisions have really been jacked up in the last 20yrs.

4hrs would be using 230mm. Fire one side and precast panel with steel roof probably falls under 20%

 

[ShawThing]

No worries, that’s what I was afraid of.
Building is type B construction due to its volume which is dictating the FRP.

I saw the reference to 170mm in a Australian Precast technical doc.

 

[ShawThing]

What is the second paragraph of 5.7.2 referring to if it is not allowing the use of clause 5.7.1 where the top of the wall is supported by a member that does not have an FRL?
Does it mean the supporting member will fail first and so allows a reduced wall thickness to be adopted for structural adequacy?

 

[Retrograde]

What is the second paragraph of 5.7.2 referring to if it is not allowing the use of clause 5.7.1 where the top of the wall is supported by a member that does not have an FRL?

That clause generally applies to industrial buildings with tilt-up concrete walls.

 

[ShawThing]

Thanks Retrograde, that's the type of building I am designing.

 

[Retrograde]

Have a read of this:

https://www.libertygfg.com/media/1923/fdn1_externalwalls.pdf

 

[ShawThing]

Thanks again Retrograde

Have been thinking about this and probably should provide more detail so if anyone can assist I can get a more informed and detailed response.

I am designing a 50m long x 20m wide portal frame building (central ridge) which will have concrete panel walls. Portal frames to be at 5m centres. On the sides the walls will be approx. 15.4m high.
At this stage thinking of having 3x 5m wide panels by 5m high on top of one another between each portal and spanning the panels horizontally. Panels will be dowelled together along horizontal joint.

First issue is panel thickness to comply with 240 min structural adequacy. Was hoping to be able to use paragraph two of 5.7.2 AS3600 to adopt 175mm thick walls but not sure if this is appropriate?

Second issue is fire tie compliance. Have had advice from a fire tie supplier that I would need fire ties top and bottom of all three panels, with the exception of the bottom of the lowest panel as it will be tied to a footing. That sounds reasonable but again not sure if that is 100% correct?

Have designed a few panel buildings before but haven't come across this situation previously. Any further advice would be welcomed and appreciated.

 

[Retrograde]

Are you casting the panels on site? Instead of having a three panels stacked vertically could you not do a single panel?

I think in your situation you can definitely use 175mm thick for fire rating.

 

[ShawThing]

Thanks for that.
Yes, panels most likely cast on site. That would make panels on sides of building 32 tonne. Mind you even two panels would probably be ok.
Was worried about the weight and the building is just off a boundary and was concerned about construction issues about maneuvering a 15.4m high panel around.
On the gable end panels will be even higher again.
Thanks for your feedback again.

 

[Frazl]

What is your guys take on clause 5.7.3 in relation to effective heights for walls with a FRL? It says the effective height to thickness shall not exceed 40, but shall not apply to walls where the lateral support is provided by an element not required to have an FRL.

For the case of a concrete tilt panel laterally supported by a PFC at the top, does this mean that this height to thickness ratio of 40 does not apply? And if so I would I just adopt 50 as the height to thickness ratio as per clause 11.1 (b)?

 

[ShawThing]

Yes, I think you could adopt a height to thickness ratio of 50 in your situation.