things to consider - anchoring steel L section with a single bolt

[greznik91]

Im designing an L section and post installed anchors that supports beams for glass.
Anchors are placed in the middle of L section. Is that OK or they should be placed higher towards flange?

Since Im dealing with an opening in the existing concrete wall - that means that I get concentrated loads/reactions on both edges of concrete walls. So that means my anchors there will be loaded more - in shear and in tension/pull out. Would you place a stiffener at the edge of each concrete wall that somewhat stabilize the rotation (torsion) of L section?

Is there any benefit to place L section upside down - flange at the bottom and not at the top?

I was also thinking about making a seperated beam for opening - so i dont get extra shear forces in anchors.
What do you think about this?
Would you go with option A or B in this case? In option B I think I ger additional horizontal shear on anchor bolts because of rotation of a beam?

 

[Deadblow]

I would also make sure that the edge distances from the concrete edge to the anchors has been taken into account. If these are post installed anchors, the small edge distances can greatly reduce the capacity of the anchor.

EIT

 

[JLNJ]

I don't think your formula for the bolt tension is correct.

Remember that the angle is trying to pry off the wall. This force is dependent on the length of the downward angle leg and what you consider the lever arm.

 

[Celt83]

agree with JLNJ.

Also do not forget to do the combined shear and tension interaction check on the anchor.

Edit: Flipping the angle puts the heel at the bottom which being more rigid then the vertical leg can reduce the depth of the compression zone and increase your resisting moment arm.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[SlideRuleEra]

Would you place a stiffener at the edge of each concrete wall that somewhat stabilize the rotation (torsion) of L section?
I was also thinking about making a separated beam for opening...

I would not use stiffeners, size the angle so that stiffener's are not needed. Consider using an angle with unequal legs (long leg on the wall) for the reasons outlined by JLNJ and Celt83.

In keeping with Deadblow's comment about edge distance, also use multiple (generously spaced and relatively lightly loaded) anchors at each attachment position. Location of existing rebar in the wall will determine where anchors can be positioned. Design to allow field relocation or omitting of some anchors.

I would not use a separate angle for the opening, just one long angle. This allows more opportunities for field changes and load sharing over several anchors. Do not depend on a single anchor positioned at a designated spot for the design to work.

http://www.SlideRuleEra.net

 

[greznik91]

Tnx for help

 

[a2mfk]

Unless you are conservatively assuming all of the shear reaction goes into your first bolt, it is very difficult to calculate how much shear that bolt will actually get. As the angle is loaded and deflects, the ends rotate upward, which will cause less shear in each fastener moving outward until there may be an upward shear instead of a downward shear.

What I like to do is take a plate and bolt it to the wall with four bolts into the jamb. Weld the angle top and bottom to the horizontal center of this plate. Now your shear is going directly into the center of that plate, and you can divide the shear evenly into each bolt. You still have the rotational tension to deal with:

Celt83 (Structural)14 Dec 18 14:50
agree with JLNJ.

Also do not forget to do the combined shear and tension interaction check on the anchor.