BOLTING TO HSS - Steel Tube Institute

BOLTING TO HSS

KIM OLSON, PE

HSS

Steel Tube Institute Hollow Structural Sections ® 2020 Steel Tube Institute. All Rights Reserved

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• Discussion of Limit States

• Bolt Types

• Proprietary Products

Agenda

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zLIMIT STATES


BOLTING TO HSS

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• Conventional bolts are desirable – but difficult due to closed nature of shape


• Flattening ends of round HSS in order to make bolted connection

• Smaller tubular structures• CIDECT DG1 and DG3

END FLATTENED CONNECTION

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CIDECT DG1


BOLTING TO HSS

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• Access to interior• Connection at end of member• Large enough for access hole

o Placed at a noncritical location

o Can be sealed and / or reinforced so the

section meets strength requirements

o Rounded corners


BOLTING TO HSS

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• Other options:• Through bolts• Blind bolts• Threaded studs• Flow-drilling• Nails• Self-tapping screws


LIMIT STATES - SHEAR

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• Bolt shear strength (J3.6) 𝑅! = 𝐹!"𝐴# 𝑛

• Bolt bearing (J3.10) 𝑅! = 2.4𝑑𝑡𝐹$

• Bolt tearout (J3.10). 𝑅! = 1.2𝑙%𝑡𝐹$

• Block shear (if at end of member)

Lindapter


LIMIT STATES - TENSION

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• Bolt tensile strength (J3.6) 𝑅! = 𝐹!&𝐴# 𝑛

• Tension pull out

• Wall distortion

LNA Solutions



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• Pull out thru the wall • Shear rupture of surface thru the thickness of the HSS

wall • Wall thickness is critical to this limit state• 𝑅! = 0.6𝜋𝑑'𝑡 𝐹$• dw defined by the diameter of the part in contact with the

inner wall.



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• Distortion - due to flexibility of wall• Similar to HSS-to-HSS chord wall plastification by treating the area defined by the bolt

group as the branch in a T-connection. • Determined from yield line theory.

• 𝑅! =&!(")

*+# , #$%$&%+-

*#𝑄. (15th Edition Manual, Eq. 9-30)

o 𝑐 = 𝑤#o 𝐿 = 𝑙#

o 𝑅! =&!(")

) '%(

/0)%(+ ,

/0)%(

𝑄.


LIMIT STATES – COMBINED LOADING

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• User Note J3.7 – if less than 30% stressed for tension and/or

shear, then combined loading can be ignored.

• 𝑅! = 𝐹!&1 𝐴#• 𝐹!&1 = 1.3𝐹!& −

(*+2(*,

𝑓3" ≤ 𝐹!&

Lindapter

zPOLL QUESTION

zBOLT TYPES


THROUGH BOLTS

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• Only bearing connections

• Flexible face + tensioning of bolt → distortion of the HSS wall → do not pretension

bolts in an unreinforced HSS. Only install snug tight.

• Snug tight of through bolt can cause problems because all plies cannot be brought

into firm contact.

• Rounds

• Holes manually drilled (or laser)

Steel Tube Institute Hollow Structural Sections ® 2020 Steel Tube Institute. All Rights Reserved 18

• Length = grip + thickness of washer +

height of nut + proper stick out (Manual

Table 7-14) – exceed stock

• Difficult to install

THROUGH BOLTING


THROUGH BOLTS

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• The load distribution in a through-bolt differs from a conventional bolted connection

since the bolt head or nut only bears on the outside of the HSS wall and not the

outside and inside. The bearing resistance of a pin is reduced from the bearing

resistance of a bolt to account for these factors.

• Section 7 of Manual – For shear loading, only LS is bolt bearing

• 360-16, Section J3.10(c) “For connections made using bolts that pass completely

through an unstiffened box member or HSS, see Section J7 and Equation J7-1” →

calculate bearing strength for a pin• 𝑅! = 1.8𝐹4𝐴5#𝑛• 𝐴5# = d ∗ 𝑡678


THROUGH BOLTS

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• 360-16, Section J3.10(c) “For connections made using bolts that pass completely

through an unstiffened box member or HSS, see Section J7 and Equation J7-1”

“unstiffened HSS member” is referring to the face of the HSS that is not confined by a bolt head and nut on either

side or stiffened by reinforcement in its void


THROUGH BOLTS

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• 360-16, Section J3.10(c) “Bearing strength and tearout strength shall be

checked for both bearing-type and slip-critical connections.” → no direction

given.

360-22 will give direction for tearout for thru bolts in HSS360-16 eqns J3-6c, J3-6d, J3-6f

Tearout – deformation considered 𝑅! = 1.2𝑙"𝑡𝐹#Tearout – deformation not considered 𝑅! = 1.5𝑙"𝑡𝐹#Tearout – LS hole, perpendicular to force 𝑅! = 1.0𝑙"𝑡𝐹#


EUROCODE TAKE

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• Eurocode (EN 1993 1-8:2010)

• 𝐹#,:6 =/.<&6."=-.

• Bending resistance of pin

• 𝑀:6 =/.<>/'."0

=-.• wel = elastic section modulus

of pin

• AISC 360-16

• 𝑅! = 1.8𝐹4𝐴5#𝑛

• Bending resistance of pin

• ???


REINFORCED HSS

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One of the most common methods for improving the

performance of through-bolt connections is to provide a

sleeve (or round tube) for the through bolt to pass through.

The sleeve is achieved by drilling a hole in the HSS, inserting

a sleeve that has an inner diameter equal to the diameter of a

standard hole for the through-bolt, and then welding the

sleeve in place.


THREADED STUDS

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• Field or shop welded to an HSS member with a stud-welding

gun.

• HSS checked for wall distortion when stud in tension

• Bolt holes in connected part must be countersunk in order to

clear the fillet weld between the stud and the HSS.

• Behave similarly to a standard bolt


SCREWS

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• AISI North American Specification for the Design of Cold Formed Steel Structural Members, Sections J4.3 and J4.4

• Shear strength• t1 = thickness of member in contact with screw head or washer• t2 = thickness of member not in contact with screw head or washer• For ⁄𝑡! 𝑡" ≤ 1.0,

• For ⁄𝑡! 𝑡" ≥ 2.5,

• For ⁄1.0 < 𝑡! 𝑡" < 2.5, Pnv shall be taken as the linear interpolation between the above

𝑃!$ = 𝑚𝑖𝑛𝑃!$ = 4.2 𝑡%&𝑑 '/%𝐹#%𝑃!$ = 2.7𝑡'𝑑𝐹#'𝑃!$ = 2.7𝑡%𝑑𝐹#%

𝑃!$ = 𝑚𝑖𝑛 𝑃!$ = 2.7𝑡'𝑑𝐹#'𝑃!$ = 2.7𝑡%𝑑𝐹#%


SCREWS

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• Tension – pull out• tc = lesser of depth of penetration and thickness, t2• 𝑑𝑤'1 = 𝑑? + 2𝑡' + 𝑡/ ≤ 𝑑'• Pull out strength 𝑃!& = 0.85𝑡%𝑑𝐹$)• Pull over strength 𝑃!& = 1.5𝑡/𝑑𝑤'1 𝐹$/


BLIND BOLTS

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• Allow installation without access to both sides of bolt.

• Proprietary fasteners• Manufacturers develop strengths & verified by ICC

reports

• A mechanism expands as the bolt is tightened to form the

contact on the interior surface – eliminating the need for a nut

to be installed.• Single sided fasteners• Toggle bolts• Expansion bolts

• Generally for shear, although some for tension conditions.

zPRODUCTS

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BLIND BOLTS

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• Hollo-Bolt - Lindapter• Blind Bolt - Blind Bolt Company• Box Bolt - LNA Solutions• Shuriken Tubular Connect• Oneside Structural Fastener from Ajax Fasteners


SHURIKEN – TubularConnect.com

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SHURIKEN – TubularConnect.com

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DIABLO™ BOLTED SPLICE

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§ Cast steel fittings that provide a hidden splice

§ HSS5.563 thru HSS12.75


DIABLO™ BOLTED SPLICE

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zPOLL QUESTION


z

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THANK YOU

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BOLTING TO HSS - Steel Tube Institute