Single Angle Connection 6

[GalileoG]

Hello all,

I am using a single angle connection to connect my supported beam to my supporting beams. I have noticed that the tables for single angle connections on CAN/CSA-S16 uses a three sides weld, the vertical side being on the angle heel. My question to you all would be: What difference would it make having the vertical side be on the toe of the angle as opposed to on the heel? Have you ever seen single angle connections where the vertical weld of the three sided weld is on the toe? Can I have the toe welded and still use the values from this table? Thanks.

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[Ron]

It's all in shear and tension....makes no difference.

 

[jberg]

I would agree with the requirement that the 3 sided weld is on the beam and not the supporting member. Not sure if CSA requires this but AISC states that for connection ductility, you can not weld completely across the top of the angle for gravity loading (see attached sketch).

JWB

 

[DaveAtkins]

I also am assuming the angle is bolted to the supporting member and welded to the supported member.

The answer to your question is no--you must weld the heel to use the table. If you move the weld to the toe of the angle, you have greatly increased the eccentricity between the supporting member (which is where the vertical reaction occurs) and the centroid of the weld group. This creates additional moment on the weld group, which probably fails the weld.

DaveAtkins

 

[phuduhudu]

But looking at Jberg's sketch it shows the angle welded to the column (the supporting member)and that it is the toe of the angle and top and bottom that are welded. I would have thought as others stated that the angle should be welded to the beam (supported member) at the top and bottom and the toe and then bolted to the column. That way the weld group takes the moments created by the offset from the centre of the angle to the face of the column and the angle outstand on the column is able to flex to allow rotation of the beam end for a simple connection.

 

[enginerding]

In AISC, see page 10-122 for the welds. The angle can be welded either to the supported member or the supporting member. But the welds must be placed as shown or the assumptions will be violated...

 

[nutte]

Clansman, can you post a diagram showing what you're talking about? I'm not sure I understand welding the heel of the angle. Do you mean running a weld down the thickness of the supported beam web?

 

[GalileoG]

Those details show a return on the top and bottom whereas I would like to weld the entire top and bottom side of the angle (angle leg to support). However, AISC explicitly says that the performance of such a detail would not be a simple shear connection. But I can't imagine why. Comments?

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[GalileoG]

Also, can someone tell me how having only a return on the top side of the angle gives flexibility?

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[nutte]

You can weld the full width across the bottom. At the top, though, you must leave it unwelded (save the return). That way, when the beam deflects, and the end rotates, the top of the connection can pull away from the support, shedding moment, and more closely reflecting the pinned end that you're assuming to have.

This is a case where more is not better.

 

[GalileoG]

Thanks Nutte.

I have seen MANY single angle connections where they use a fillet weld all around on the leg to the supporting beam. I suppose this type connection is not right.

Also, would you prefer the three sided weld with the vertical weld on the heel or the weld shown on the PDF file that was attached? (vertical on toe, return on top, full on bottom)



Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[jberg]

Thanks enginerding,

I did not have my Code with me at the time, but that was the page I was looking for to explain the types of single angle connections.

JWB

 

[nutte]

Welding all around is indeed wrong for this connection.

If you weld the heel, there can be no flexing of the angle, so you would not have a pinned connection like this type assumes. Therefore, do not weld the heel. Weld the toe, like AISC says.

 

[GalileoG]

Nutte, does a single angle connection shown on AISC offer more flexibility than say a shear tab connection (knife plate)?

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[nutte]

I would think so, but how much more, I'm not sure. I'll have to let someone else chime in.

 

[BAretired]

A shear tab connection, welded to an unyielding column flange and bolted to the web of the supported beam, offers very little flexibility unless the bolt holes are slotted.

BA

 

[GalileoG]

BAretired,

I am sure you are familiar with the table on pg. 3-69 (yellow coloured pages) on CAN/CSA-S16 (Ninth Edition.) Do you think that this connection is less diserable to that shown on AISC tables? (detail was attached to enginerding's thread.) Your thoughts?

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[jberg]

It is true that a shear tab welded to a "rigid" support does not offer much flexibility as BA and Nutte mentioned, but in the 13th Edition AISC Manual, I believe there is a maximum limit on the plate thickness. My understanding is that this allows the bolts to "plow" through the plate and ensures that the plate yields before the bolts fail in shear.

This requirement gives the connection the flexibility necessary for a pinned condition.

I do not have my Code with me, but tomorrow I will scan the appropriate pages.

JWB

 

[BAretired]

Clansman,

I don't think either detail is very flexible. I guess I'm not a big fan of single angle connections but I have allowed them when reactions are small. For high reactions, I prefer double angle connections with weld placed only on the edges of the outstanding legs. That is flexible.



BA

 

[jberg]

Sorry for the delay, but attached is the discussion in Modern Steel Construction about single angle and single plate connections, for what it is worth.

We typically spec 2L connections but there are many situations when the reactions are small and constructibility issues make using a 2L connection next to impossible, so in those cases a single angle or single plate is a better solution.

JWB