Through-Bolting to HSS Soffit Application 1

[Givemeamoment]

Hello,
Where can I find design examples or guidance of how to through-bolt an HSS member from the underside to the plate above with a nut? Or blind bolts? And where can I find information for bolts less then 5/8" since it's not given in AISC? I've never designed for an overhead application. I'm designing a hanging architectural frame where I'm checking if a pan head through bolt with a nut (or blind bolt) would be feasible (it's preferred to not see any bolt hex heads from the bottom and everything be flush). Any guidance is much appreciated, thank you!

 

[dik]

Can you weld? Through bolts taking any type of load is not a good practice for HSS.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Givemeamoment]

dik, thank you for your response, no field welds. It makes sense that it's not good practice, are there any references you would recommend I could read up on for through bolting HSS? Or what about using blind bolts in an overhead application? Thanks!

 

[JLNJ]

Have you looked through the Hollo Bolt website?

 

[Givemeamoment]

JLNJ, yes thank you! I contacted the local representative to see if they could give me design values.

 

[STrctPono]

This is the product that I've always used in the past when blind bolting to HSS members. They post their safe working loads under the technical information. The dimensional information is a bit incomplete in my opinion and I have had to contact them in the past to get further information on some of the dimensions that were not clear to me.

Link

 

[Tomfh]

I prefer to through bolt than use hollobolts. Welded sleeve are good if you’re concerned about crushing the tube.

 

[Enable]

I think the blind bolts mentioned above should serve well. But just to add another option to the mix, AISC Design Guide 9 (HSS Sections) offers this gem:

 

[Givemeamoment]

STrctPono, thank you for the link to the box bolt website. I like how they have a 1/4" bolt available whereas Lindapter only has an M8 bolt as their smallest available size. On the lna box bolt link, do you know what the asterisk* means after the 1/4" size?

 

[Givemeamoment]

Enable, that is a nice find, thank you for sharing. I will have to look into that!

 

[Givemeamoment]

Tomfh, I would like to use through bolts but I'm a little concerned about nut pull through. And the architect would prefer a flush finish from the underside, so I would have to use a flat head through bolt, where I'm not sure if those are available. My through section is 4inches plus a 1/4inch plate. Do you have any references or recommendations where I could read more about requirements for through bolting to HSS? AISC 14th Section 7-13 doesn't give enough details in my opinion as far as the required length past the through section and nut/washer requirements. Thank you!

 

[Enable]

Is there a particular reason why you desire to through-bolt so much, say as opposed to the other one-sided options? Through-bolting carries significant risks of the installer over-tightening and crushing the wall; typically internal restraint would need to be provided to mitigate this risk.

If hell bent on through-bolting I suppose you could do a variant of the detail I posted above. That is, weld a nut on both faces and use B7 threaded rod or the like to pass through. Field weld the side to be flush, grind smooth and use touch-up paint. Nothing exposed at the visible surface but it's a through bolt in a sense.

But for reading purposes:

Thread Here: Inserting steel tubes into the HSS to mitigate the over-tightening

Steel Institute Article here: Describing items mentioned in above thread in slightly more detail

From the reference I pulled the nut detail from:

Rather than using “blind bolts” (or a “single-sided bolting system”) when bolting an
element such as a beam end plate to a RHS column, it is possible to use long bolts or
threaded rods which pass all the way through the RHS column member. Thus, both the
head and the nut of the bolt (or threaded rod) are on the outside of the RHS. This is accept-
able in a shear connection if the bolts are only snug tight (i.e. not fully pretensioned).
Single shear plate connections have been tested by Sherman (1995) with bolts snug tight
and fully pretensioned, and both have performed adequately. The connections with snug
tight bolts had the same ultimate capacities and eccentricities as those with pretensioned
bolts. However, at working loads, pretensioned bolts produced larger eccentricities (to the
contraflexure point where negative moment changed to positive moment).
In many connections the bolts will be fully pretensioned, especially if the bolts are liable to
go into tension. With full pretensioning, through bolts should only be used if the bolt inside
the RHS walls passes through a spacer tube or pipe. This spacer tube should have a
length equal to the inside depth of the RHS so that when the bolt is tensioned the spacer
tube is placed in compression, hence preventing the flexible faces of the RHS from being
pulled inwards and thereby being deformed during the erection process. Section 3.5.6 of
CIDECT Design Guide No. 6 (Wardenier et al. 1995) gives some fabrication advice for such
joints.