steel connection 6

[wrxsti]

In AISC Design Example K.1 - Welded bolted wide tee to hss column

Wide Tee welded to column and bolted into a W section.

For bolt capacity they use eccentricity

The configuration resembles a conventional configuration for single shear plates

however for conventional configuration on single shear plates eccentricity can be ignored.

 

[CANPRO]

I'm not sure what the question is in all of this, but I take issue with this statement:

however for conventional configuration on single shear plates eccentricity can be ignored

This is false. If you're designing single shear plates without any consideration for eccentricity, you're doing it wrong. If the shear tab is welded on one side and bolted on the other, either the bolt group or the weld must resist the eccentricity. I'm not too familiar with AISC but I just checked their tables (Table 10-10a) for single shear tabs and they most definitely account for eccentricity.

 

[wrxsti]

If the shear tab is welded on one side and bolted on the other, either the bolt group or the weld must resist the eccentricity.

Understood the said example goes on to analyzing the weld as concentrically loaded a lieu the bolts which were analyzed as eccentrically

However, for single plates the manual does state no eccentricity for ' conventional configuration '.

I am trying to find literature to show if the eccentricity is now applied on the weld =)
but it is encompassed in design tables within AISC, governing case i would not suspect to be weld to even back check?

the only example i have is the spreadsheet from steel tools for beamtab (updated to aisc 13)

which does not account for any eccentricity for welds

and only eccentricity in bolts for non-conventional configuration

 

[BAretired]

I don't like flare-bevel groove welds at the corners of the HSS and I don't like the appearance of the tee flange projecting beyond the HSS. Prefer to use double angles or tee flange contained within the wall of the HSS.

BA

 

[strucbells]

It's less that eccentricity is "not applicable" for shear tabs but more that accounting for the eccentricity is "baked into" the procedure in the steel manual through limitations of the plate size and other geometry:

https://www.aisc.org/globalassets/modern-steel/archives/2006/10/2006v10_simpler_shear.pdf

So, if you are meeting the same limitations with the stem of your WT-, and connecting it in a similar manner to the column, you may be able to justify through engineering judgement that it will behave similarly and that eccentricity can be "ignored" due to bolt ploughing, etc. However, I'm not sure off hand if there is justification for that in the code. I'd just design it with consideration for the eccentricity in the bolts.

 

[CANPRO]

Ok, I think I understand your question. I don't know the details of how the AISC table was generated, but it sounds like the assumption is that welded side of the shear tab is flexible (vs rigid). In reality the work of resisting the connection eccentricity will be shared between the welded side and bolted side in proportion to the rotational stiffness. For design purposes we assign that eccentricity to one side of the connection only. See picture below - this is from the CISC handbook...they provide (2) tables for single shear tabs based on flexible vs rigid supports. There is a brief explanation of the difference between the two and there is a reference at the bottom of the page for some further reading if you're interested.

 

[JoshPlumSE]

It's less that eccentricity is "not applicable" for shear tabs but more that accounting for the eccentricity is "baked into" the procedure in the steel manual through limitations of the plate size and other geometry:

https://www.aisc.org/globalassets/modern-steel/arc...

Yes, what strucbells said!

I should also point out that it's less "baked in" than it used to be. The AISC 15th edition steel code requires that you consider eccentricity for single plate shear tab connections that meet the "conventional" configurations (see table 10-9 and pages 10-87 through 10-91. It's just that you can use a reduced eccentricity for those conventional connections. Whereas I believe the 13th edition allowed you to ignore the eccentricity provided you met their definition of "conventional" shear tab connections.

 

[wrxsti]

Muir, Larry S.; Thornton, William A. (2011). "The Development of a New Design Procedure for Conventional Single-Plate Shear Connections," Engineering Journal, American Institute of Steel Construction, Vol. 48, pp. 141-152.

Conventional single-plate shear connections are common and economical connections. The design procedure outlined in the 13th edition AISC Steel Construction, (AISC, 2005a), Manual relies on the bolt shear values given in the 2005 AISC Specification for Structural Steel Buildings (AISC, 2005b). The nominal bolt shear values listed in Specification Table J3.2 have historically been 20% lower than the theoretical bolt values. This reduction was provided to account for uneven force distribution among the bolts in end-loaded connections, such as bolted lap splices. The reduction served the secondary function of providing an additional factor of safety for all bolted connections designed in accordance with the Specification. The design procedure for conventional single-plate shear connections contained in the 13th edition Manual relied on this reduction to justify the practice of neglecting eccentricity in the bolt group for most configurations. The 2010 AISC Specification increases the nominal bolt shear values, necessitating a revised design procedure for single-plate shear connections in the 14th edition AISC Manual. This paper outlines the revised procedure.

 

[wrxsti]

the next question is if the weld is not sized at 5/8tp does it void the configuration?

 

[KootK]

It voids the extended shear tab configuration as that is predicated upon the welded joint developing at least the capacity of the connected plate material.

 

[wrxsti]

wait why only extended?

 

[KootK]

Using recent AISC provisions, it applies to the conventional configuration as well and, presumably, for the same reason. Cheap insurance to guarantee that, if things go south, it's not the weld's fault.

 

[wrxsti]

Muir, Larry S.; Hewitt, Christopher M. (2009). "Design of Unstiffened Extended Single-Plate Shear Connections," Engineering Journal, American Institute of Steel Construction, Vol. 46, pp. 67-80.

As stated previously, the plate acts as a fuse to protect
both the bolts and the welds from rupture, thereby allowing
the moments to redistribute in an acceptable manner.
In order to safeguard the weld, the plate must yield prior
to the weld fracturing. Prior to the 13th Edition AISC Steel
Manual, AISC required that the welds to the support be sized
as at least w of the plate thickness. This requirement was
developed to ensure that the plate would yield before the
weld yielded (Astaneh, 1989). In the latest procedure, this
recommendation has been modifi ed, and the new procedure
recommends that the plate be sized to yield before the weld
ruptures. This is a more logical approach, as weld yield is
not a well-defined limit state, and joint separation will not
occur until the weld ruptures. The modifi ed requirement
calls for the weld be equal to or greater than s of the plate
thickness.

 

[BAretired]

Looks like AISC is having trouble making up its mind.

BA

 

[wrxsti]

Looks like AISC is having trouble making up its mind.

i know right, ive seen some 9th edition examples with eccentricity in both bolt and weld calculation
for the same configuration

 

[r13]

I think the underlined limit on applicability is intriguing.

 

[evo10]

r13, yea thats the case for bolt ploughing as strucbells mentioned in his post above

actually all the case 3 to 6 are to accomodate ploughing

Hewit, Christopher M. (2006) "Simpler Shear Connections: Design procedures for single-plate shear connections have been expanded in
the new Manual to incorporate a wider variety of geometric parameters," Modern Steel Construction, October 2006

Bolt plowing is the unique feature that allows shear tabs to function well beyond the rotational requirements of simple shear connection and is critical to understanding the performance of this connection type.

 

[BAretired]

STD means standard? Should be Std. STD, using all upper case implies three words. I had to look up SSL...supposedly stands for Short Slotted Holes. That's a misnomer too. Should be SSH (opposite of HSS). I don't know why people can't be bothered typing out the words. Is it so much trouble? Who goes around thinking, ah yes, good old SSL holes? Just a day or so ago, we had IWP. Turned out it meant insulated wall panel. Who knew? Some terms are commonly understood. HSS is one of them. SSL is not. RCMP (Royal Canadian Mounted Police) is well known in Canada, but probably not too well known in India. Consider your reader. If you're not sure, type it out. It won't kill you!!

BA

 

[r13]

Correct.

 

[r13]

"Simpler Shear Connections
Design procedures for single-plate shear connections have been expanded in
the new Manual to incorporate a wider variety of geometric parameters.
BY CHRISTOPHER M. HEWITT (2006)"

Here is the cited article. Link