Bolted Sleeve Connections with Hollow Sections

[Vigardo]

TL;DR

What code should be used for designing Bolted Sleeve Connections for Circular (or Rectangular) Hollow cross-Sections?

Dear experts, thanks in advance for your kind help!

I have not found any provision or rule for designing bolted sleeve connections in EC1993-1-8 (Eurocode 3: Design of steel structures - Part 1-8: Design of joints) like the one shown in the figure:

I have just found some research paper about this kind of useful connections for Circular Hollow Sections: https://www.researchgate.net/publication/340793459_Bearing_failure_in_bolted_sleeve_connections_with_circular_hollow_sections_under_compression

Would you help me to find the appropriate design code? Any help is highly appreciated!

 

[Lnewqban]

You should be able to find some information here:
https://www.astm.org/

https://www.eng-tips.com/threadminder.cfm?pid=507

 

[Vigardo]

Thank you very much!

I´ve found this thread about Bolting through Hollow Square Sections (HSS) in the eng-tips forum you´ve indicated. There are provisions for Through-Bolting to HSS in Section 7-13 of the AISC 13 (pages from 885). More about connecting HSS members with through-bolts here.

However, what about Bolting through Circular Hollow Sections (CHS)? In other eng-tips thread, there is a question about through bolting CHS... but without a successful response. Another relevant thread about Tube Slip Joint Moment Connection with CSS is this one, but again it lacks any valid reference to a construction code.

I´m trying to bolt two tubes together (one slightly wider than the other) using through bolts. Please, let's suppose that in the figure the 0.9 mm thick tube had another one fitted inside with a slightly smaller diameter.

Any code reference would be highly appreciated!

 

[Lnewqban]

You are welcome.
What kind of load is that connection supporting?

 

[Vigardo]

Sorry, in principle, it just must withstand tension and compression along the axis of the tubes. Thanks!

 

[Lnewqban]

In that case, I would say that the 0.9 mm wall of the tube is the weakest link to consider regarding deformation of the holes under tension and compression loads.
Staggering those holes, as well as reducing the size of the bolts may help.

 

[jrmichler]

I'm not aware of any code that covers this exact situation. There is good information if you search design of bolted joints and design of riveted joints. The short version is that several calculations are required:

For each tube:
Crushing under the bolt
Shear failure of the tube
Tensile failure of the tube

For the bolt:
Shear of the bolt
Slippage of the joint

This figure, from Aircraft Structures, by Peery, shows most of those failure modes. The tensile failure of the tube is in a separate figure.

These calculations are common in metal aircraft construction. Substitute rivet for bolt, and design each joint for equal strength of all failure modes to get the best (usually lowest weight) design. The aircraft design code, FAR Part 23, specifies the design loads, but does not specify how to calculate the stresses.

You will also need to find appropriate safety factors.

 

[Vigardo]

In that case, I would say that the 0.9 mm wall of the tube is the weakest link to consider regarding deformation of the holes under tension and compression loads.
Staggering those holes, as well as reducing the size of the bolts may help.

I´m sorry, I borrowed the figure somewhere. For example, the wall thicknesses of my connections would range from 3 to 10 mm and the diameters from 10 to 25 cm. The relative bolt size should be also much smaller than it can be seen in the figure. In any case, I´ll take into account your recommendations.

 

[Vigardo]

Thanks @jrmichler for your detailed response! I´m already aware of such failure mechanisms. It is good to know that Aircraft Structures (by Peery) deals with all of them.

In ASCE 13 (page 887, link above), there are provisions about Nailing to HSS, which in essence is what I´m trying to do, but using bolts instead of nails. In Packer 1996, it can be seen a telescopic arrangement using nails as fasteners (see below), some formulas for bearing strength (Rn) are also given. However, this is a initial research study so caution is mandatory.

Source: Packer, Jeffrey A. (1996). Nailed Tubular Connections under Axial Loading. Journal of Structural Engineering, 122(8), 867–872. doi:10.1061/(asce)0733-9445(1996)122:8(867)

By the way, I´m sorry, it seems that HSS in ASCE 13 stands for Hollow Structural Sections, i.e. not for Hollow Square Sections, as I said above. So, the provisions provided in page 886 for through-bolting to HSS should be also valid for Square, Rectangular or Circular HSS:

However, I haven´t read anything about how the curvature of the CHS would affect joint behaviour. Intuitively, it should be different whether it is Squared or Circular, shouldn´t it?

Perhaps, instead of through-bolting I would use the provisions for Snug-Tightened joints:

It seems that all the provisions related to bolted joints in are indicted in pages 878-879:

-RCSC Specification for Structural Joints Using ASTM A325 or A490 Bolts (sections 5.1-5.3, pages 1938-2030 in ASCE 13 pdf). Particularly, in pages 1977-1988, provisions are given for design shear and tensile strengths, bearing strength at bolt holes, slip resistance, and tensile fatigue.

- In Section J3 from (pages 1579-1588), minimum bolt pretension, nominal stresses, hole dimensions, minimum edge distances, etc.

Unfortunately, none of them mention anything about CHS... Should I just use such formulas as a first approximation to the "bolting to a curved surface problem"? It seems quite evident that tightening flat bolts to a curved surface will distort cross-section. There may exist curved washers to prevent this undesired effect?