Shear Tab with Minor Axial Force

[WiSEiwish]

Hello,

If I am designing a beam as a simple beam with single-plate connections on either side, how do I account for the inevitable minor axial forces that will exist?

I am looking at a simple manufacturing building supported by steel columns. There is cross bracing to provide lateral stability in addition to there being a metal deck on the roof which I am considering a flexible diaphragm. The deck support is open web steel joists and on the perimeter there are WF beams. I am designing the perimeter roof beams as simple beams thus they are not designed to take axial load or bending moments. The typical connection of these beams to other beams or columns are conventional single plates and extended single plates. During the design and analysis of the structure I'm finding that these perimeter beams have a small amount of axial load (1.9k max). I know that the beam itself is good for that load, but I don't know how to take that into account when I'm looking at the connection.

Any thoughts/comments?

Thanks.

 

[wannabeSE]

You don't mention anything about the connection you propose. 1.9 kips is not much, and probably won't be a problem unless it is a wimpy connection or already loaded with gravity close to its capacity. However, If you do steel design, it is important to know how to design these connections. Otherwise, you can not design a simple collector connection. AISC's Seismic Design Manual has a good design example. But I don't know if it is worth buying the book if you do not do seismic design. There is also a June 2005 Steel Tips on "Design of Shear Tab Connections for Gravity and Seismic Loads" that can be downloaded at

http://www.steeltips.org/.

It has been a while since I read the Steel Tip. I like the example in the Seismic Design Manual example a lot more.

 

[JoshPlumSE]

There is a book, "Handbook of Structural Steel Connection Design and Details" by Ankar Tamboli. I believe this book suggests that when the axial load is small you should just combine it with the shear load Veq = sqrt (V^2 + P^2) and continue designing it as a pure shear connection. That should be fine when the shear force dominates the behavior. I think that should be the case for your connection.

For connections where the axial and shear on much closer in magnitude that method may not be sufficient. In cases where the load gets large, it may be necessary to use an Moment + shear + axial force interaction formula for plate yielding or plate rupture. Refer to equation 10-5 of the AISC 14th edition manual for some guidance. They leave axial force out of their interaction equation. So, you would have to add it in using some engineering judgment.