Kicker Stair Support
Kicker Stair Support
(OP)
Hey Gentlemen,
I'm reviewing a stair submittal sent by the fabricator. The top landing is anchored to a concrete wall by a kicker. My goal is to check the adequacy of the connection (in particular the bolts anchoring into the concrete). As you can see by the attached pic the bolts are not eccentric. An example in my book has a tension-shear interaction check, but the bolts are eccentric, and the centroid can easily be found. Does anyone have any examples or guidance for the senario I have here. Plz see both pics, help is much appreciated.
I'm reviewing a stair submittal sent by the fabricator. The top landing is anchored to a concrete wall by a kicker. My goal is to check the adequacy of the connection (in particular the bolts anchoring into the concrete). As you can see by the attached pic the bolts are not eccentric. An example in my book has a tension-shear interaction check, but the bolts are eccentric, and the centroid can easily be found. Does anyone have any examples or guidance for the senario I have here. Plz see both pics, help is much appreciated.






RE: Kicker Stair Support
RE: Kicker Stair Support
Are you asking for advice on the anchor design or on the analysis of the system?
RE: Kicker Stair Support
RE: Kicker Stair Support
However, you can sum forces/moments about the neutral axis of the bolt group and resolve this into compression and tensile forces on your bolts. Anchors above the n.a. will have tension and shear and the bolts below will have compression and shear.
I caution you this:
The area load on the landing will amount to reactions at the ends of the C10.
On the left side of the C10, the force will wind up in the knee brace. The bottom pair of anchors in the wall should take the full shear force resulting from the knee brace.
On the Right side of the C10, the shear will be taken by the top pair of bolts.
I would NOT share the shear force amongst all bolts.
RE: Kicker Stair Support
DaveAtkins
RE: Kicker Stair Support
I was assuming pairs of bolts as far as "into the page".
RE: Kicker Stair Support
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Kicker Stair Support
I don't see by the pic that the bolts are not eccentric. Not eccentric to what? Please explain what you mean.
Whose expansion bolts are being used and how deep are they embedded? What is the minimum spacing between bolts according to the manufacturer? 3" seems too close to me for the upper two which carry most if not all of the tension.
Maybe through bolts should be used, at least for the top two.
BA
RE: Kicker Stair Support
As for your book example, I'm fairly sure that the eccentricity referenced is actually the distance of each bolt from the point of rotation of the knee brace. OK...now where's the point of rotation? It can be anywhere from the bottom of the knee brace to the vertical center of the bolt group. It will also depend on the bolt spacing and stiffness of the vertical member.
Perhaps the easiest analysis method would be to consider the vertical member a continuous beam with 5 support points and an applied moment at 2/3 the distance from the bottom.
Another way is to use the AISC base plate approach, considering your vertical leg to be a base plate.
RE: Kicker Stair Support
RE: Kicker Stair Support
I had the same thought....but I was so confused about the eccentricity that i didnt even know how to ask a question. I mean, eccentricity is not an intrinsic trait. Some have accused me of being eccentric, with reference to no physical point, but we can't do that here can we?
RE: Kicker Stair Support
I am not comfortable with the two top bolts being expansion bolts, especially at 3" centers because the rupture cones overlap. I would prefer to see either through bolts or a weld plate anchored in the wall using headed studs. Then the attachment angle could be welded to the weld plate on site.
BA
RE: Kicker Stair Support
I still don't know what he meant by eccentricity, but the sketch seems clear enough.
BA
RE: Kicker Stair Support
Pad- Yes, I think "kicker" is used to too often.
RE: Kicker Stair Support
The only "e" I can think of is that which is out-of-plane.
That would exist, no?
RE: Kicker Stair Support
Michael.
Timing has a lot to do with the outcome of a rain dance.