PURLIN CLEAT HOLE DIM AS/NZS

[Veer007]

Hey Guys, I have the case that I'm using 12mmØ bolt grade 4.6s/pb1230 for purlin connection cleats, what my concern is I have to use 6mm tolerance in steel connection plate, which is fine?

Also, the below hole values seems so high like 22mm dia hole for 12Ø bolt.. Please let me know your thoughts on this

Also the bolts should be galv or can be plain?

Thanks in advance!!

 

[rowingengineer]

We should all take a few seconds to read as/nzs4600, unless your chicken

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[Agent666]

Noted. Its all in there. Different rules for NZ and AU.

 

[human909]

I've heard Australian Engineers make Agent666's argument that our industry standard purlin connections are fundamentally non compliant with the code. E.g. AS4100 provisions for hole size which limit to +2mm oversize, and the bracing rules which prohibit anything which allows slip to be a bracing restraint.

As an Australian I don't have too much come back to that. It does seem that NZ codes and implementation are more rigorous than AU in many areas and there usually isn't much justification for AU's short comings except 'it has worked so far'. When it comes to restraints, having a little more than >1mm play in a lateral restrain for LTB doesn't strike me as a problem in most circumstances. But I do see it as a sloppy near enough is good enough approach.

 

[Tomfh]

AS4600 extract:

What about the cleats though? They are >3mm, so shouldn't AS4100 apply, i.e. 14mm holes for M12 bolts?

Regarding lateral bracing and rotational bracing from purlins - how best to interpret the use of purlins as restraints? Do we accept that a purlin with slotted hole can provide lateral resistance? And that a fly braced purlin does prevent rotational slip, even though the bolt could slip 10mm or more?

 

[Agent666]

Regarding lateral bracing and rotational bracing from purlins - how best to interpret the use of purlins as restraints? Do we accept that a purlin with slotted hole can provide lateral resistance? And that a fly braced purlin does prevent rotational slip, even though the bolt could slip 10mm or more?

Therein lies the issues with AS4100. Purlin can obviously be designed to provide restraint; NZ code has some other requirements for this that extend beyond providing the 'moment' connection to cleats.

In the 1998 commentary to AS4600 the following was said... obviously, they have not kept up with updating the commentary. But the same applies even today 20+ years later regarding tensioning of bolts like I posted previously from NZS3404.

Despite what AS4600 states, slotted holes are not standard here in NZ.

 

[hokie66]

Purlins are more or less a commodity item. Is this the guide you use selecting purlins in New Zealand?

https://d1ki6btnkpblpf.cloudfront.net/1001/mc-structural-guidejunel2020.pdf

 

[Agent666]

There are more or less three main players, the one you linked, dimond, and steel and tube. I've only ever used the dimond and steel and tube ones though.

Edit - we either select from charts such as you posted or design in software (typically using Purlin, out of I think Sydney University, not many people seem to have it though)

 

[hokie66]

I don't know what all consultants do in Australia, but the ones I have been associated with use the load tables. The load tables were produced not only with software, but are supplemented by full scale testing.

 

[Tomfh]

Therein lies the issues with AS4100. Purlin can obviously be designed to provide restraint; NZ code has some other requirements for this that extend beyond providing the 'moment' connection to cleats.

What does NZ require for a purlin to be considered a lateral or a rotational restraint?

Also, do you think +6mm round holes in purlin cleats complies with AS4100/4600 as far as AS4100/4600 is concerned? I know NZ forbid it , but I can’t figure out what the code are saying for Australia. Are the 18mm round holes in cleats code compliant?

 

[Agent666]

The referenced DCB is attached.

 

[tristan861]

When installing flange brace underneath the purlins. Would the flange brace transfer axial loads to the purlins?
so we can make their holes slotted so the(purlins)dont buckle?. Does this make sense??