Shear flow ?
Shear flow ?
(OP)
Folks,
This may be a really simple, stupid question....
I have a situation where I need to connect 2 single angles (toe-toe) to create a U shape.
I think the weld should just be to keep the two members together, preventing them from separating. A skip weld maybe.
A single angle in bending unrestrained)....a case of two drunks leaning on one another? How do you design this?
This may be a really simple, stupid question....
I have a situation where I need to connect 2 single angles (toe-toe) to create a U shape.
I think the weld should just be to keep the two members together, preventing them from separating. A skip weld maybe.
A single angle in bending unrestrained)....a case of two drunks leaning on one another? How do you design this?






RE: Shear flow ?
Whats the orientation of the two angles once welded in relation to the load path.
If it was me I would choose a continuous weld.
desertfox
RE: Shear flow ?
Imagine a U shape, comprised of 2 angles. As if a Channel is bending in weak axis.
Loading is downwards (connected legs - tension flange)
One of the things I will have to check is local buckling in the outstanding legs.
RE: Shear flow ?
RE: Shear flow ?
There is apparently a reason that a channel can't be used here?
Be aware of a strong potential for rust staining on the exterior (assuming exposed)with this design...don't let that come back to bite you in the a$$.
RE: Shear flow ?
RE: Shear flow ?
RE: Shear flow ?
To answer the question directly, though, as everyone else has said, there is no shear flow. You're just joining the sections to make a single U.
One thing I have done in the past is have the edges prepped for a CJP for the entire length. I provide a skip weld and then the spaces in between the welds get filled in with something like bondo or a metal filler with SS chips if you are using SS. The CJP should be ground flush so that when the filler is used you can apply a coating for rustproofing and you never know it isn't a single, solid CJP.
RE: Shear flow ?
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Shear flow ?
The wall/masonry itself may take a good portion of the lateral force as it might be significantly more stiff than the "U".
I always hate to have welds in bending so if there is any chance that the vertical legs of the "U" would move relative to one another, I'd also suggest occasional vertical stiffeners to tie the two vertical legs together a bit.
RE: Shear flow ?
In India, elevator shafts require hoistways to be separated by 2 hour fire rated walls. There will be 100mm thick AAC block separation wall.
The contractor wants to use this U shaped steel member that will be set on the slab formwork on one side and bear on the shear wall (either in a pocket) or directly if the wall above is not cast.
This will also enable to attach the elevator guide rails to the sides of the U shape. Why a channel is not being used is beyond me.
The way I am designing this is such that the steel member will act only as formwork and there will be a 8" wide x 8" deep concrete beam spanning the width of the elevator. That way, the steel member will not need to be fire-proofed.
RE: Shear flow ?
I agree with JAE that the wall will take up most of the lateral loading, so the shear flow would be negligible and perhaps nonexistent.
Not a fan of using fillers for weld gaps. They tend to hold moisture and promote corrosion. Just use a seal (cap) weld if you only do a skip CJP weld.
RE: Shear flow ?
RE: Shear flow ?
RE: Shear flow ?
Have you seen a lot of problems come from that type of detail? We've done that detail after getting push back from fabricators about the amount of weld and the architect wants to see what looks like a continuous weld. When we do that, we typically coat the entire thing with tnemec paint.
If that's a bad detail, though, it's definitely good to know.
RE: Shear flow ?
Look at this link and go to design of welds 3.3.5
http://np
It talks about intermittent butt welds and fillet welds and indicates area's where these should and should not be used.
Personally I don't know what sections your considering but I would be tempted to weld the angles together with a backing strip.
desertfox
RE: Shear flow ?
I don't like continuous welds on angle legs, as the whole thing is likely to distort. And it is a moot point in your case, as the angles are just for temporary support. Intermittent welds would be fine.
Don't you have concrete or masonry walls at both ends of this beam? Why not precast it and eliminate the need for temporary support?
RE: Shear flow ?
If there is any fatigue in the joint then intermittent welding is a non-starter:-
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RE: Shear flow ?
The weld carries a continuous moment directed parallel to the member. This is necessary in order to prevent the combined section acting as two separate angles as suggested by Toad Jones.
Under lateral load, the shape has a tendency to rotate because the load is applied above the shear center.
BA
RE: Shear flow ?
RE: Shear flow ?
RE: Shear flow ?
1. There is no lateral loading, since this member is only acting as formwork.
2. The member is symmetrical once made composite by joining the legs.
My concerns are:
What are the forces acting along this weld that will make this member composite. Once composite, this is akin to channel in weak axis bending.
Taking 2 angles, which want to rotate and trying to connect them together is the issue. What are the forces acting at the interface?
RE: Shear flow ?
Assume two angles L4x4x3/8 created to form a 8" wide x 4" deep U shaped member.
Assume that the 2 angles are connected by a 3/16" thick x 0.5" wide member to mimic a weld.
Assume a loading of 0.5 klf and span of 10 ft.
RE: Shear flow ?
RE: Shear flow ?
They will act like a normal beam when welded together because your loading through an axis of symmetry so there will be no twisting, therefore the weld will be subject to a moment and shear stresses similiar to that of a normal beam.
htt
RE: Shear flow ?
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Shear flow ?
where V = Shear at the support, I = M.I. of the two angles about minor axis of the (overall) section, and Q = moment of area of one angle about the c.g. of the (overall)section, i.e. about the weld axis.
RE: Shear flow ?
Assume:
.1 Vertical legs carry all of the load.
.2 Load is uniformly distributed over the horizontal legs.
.3 Span is 8"
M per foot = 500 * 8/8 = 500"#/'
S = 12(3/16)^2/6 = 0.0703 in^3
f = M/S = 7,111 psi in 3/16 plate.
BA
RE: Shear flow ?
Q = moment of area of one angle about the shear center / weld axis.
RE: Shear flow ?
Quantifying exactly how much weld is required depends on your definition of acceptable spread in the joint.
Cheers
Greg Locock
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RE: Shear flow ?
I understand what you are saying, which is what I am concerned about too. In my OP, you will see the reference to two drunks leaning on each other.
RE: Shear flow ?