## Design of an Angle as a Beam

## Design of an Angle as a Beam

(OP)

How do I go about designing an angle as a beam (a short one of course)? My angle is loaded on the inside face of one of the legs (not an upside down L where stiffeners could be added) so it is not stiffened, and it is not braced the full length. I've looked through the LRFD (2nd Ed) and it has equations and tables for Channel sections and I-beams, but not angles. Can anyone point me in the right direction? Do the same equations apply?

## RE: Design of an Angle as a Beam

## RE: Design of an Angle as a Beam

I missed it, and it's even in BOLD LARGE TYPE.

## RE: Design of an Angle as a Beam

## RE: Design of an Angle as a Beam

- the best answer I have ever read in this forum.

## RE: Design of an Angle as a Beam

On 6-284 (LRFD 2nd ed) it defines "b" as the full width of angle leg with tip in compression. Of course it does not show this pictorally, so I am a bit confused.

If I have a 6x4x3/8" angle with the load applied on the inside face of the 4" leg with the 6" leg pointing up

(loaded as an "L" instead of an upside down L), what is my "b" dimension? I would guess that b=6", since it is used in the b/t equation and t is the thickness of the angle.

Likewise if my angle were upside down b would be 4" right?

## RE: Design of an Angle as a Beam

## RE: Design of an Angle as a Beam

That is a lot of the problem with angles. The geometric axes do not coincide with the principal axes. If you have a leg pointing vertically and a load pointing parallel to the leg, the angle will still deflect out of plane, even though there is no load out of plane. That complicates the design equations, as you can see in section 5.3.

## RE: Design of an Angle as a Beam

It was a tough go the first time, but I think I've got the hang of it. Now I'm just trying to create a MathCad worksheet to be able to easily do these calculations in the future which I think I've just about got done.

Thanks for all of your help!

## RE: Design of an Angle as a Beam

Using my "b" b/t is always a large number, which does not make since given the way the equations are written (comparing it to decimals of numbers).

So my "b" cannot be right.

I had, b=6"

for 6x4x3/8 with 6" leg up and in compression. Guess I do still need an explanation after all. Why can't they just illustrate the dimensions instead of trying to describe them? It's frustrating.

If you know of some place that shows the dimension pictorally, or how to better describe "b" so that I can understand please let me know.

## RE: Design of an Angle as a Beam

Q=1.34-0.761*(b/t)*sqrt(...

OOPS! I think I just found my mistake writing this out. I had the last part as "sqrt(E/Fy)" but for this ONE case it's sqrt(Fy/E). How sneaky!!!

It's OK now. Guess I did not need help afterall.

## RE: Design of an Angle as a Beam

When the angle is oriented such that it looks like an upright "L" in profile and the load is directed vertically downward (parallel to the vertical leg toward the bottom), the angle will deflect down and to the left. This puts the angle tips in compression and the heel, or corner in tension. If the load were reversed and pointed upward then the angle would try to deflect up and to the right putting the tips in tension and the heel in compression. You have to remember that angles deflect perpendicular to the minor principal axis, not about the geometric axes. If you think in terms of this and picture your loading it helps to understand whether the tip is in compression or tension.

## RE: Design of an Angle as a Beam

DBD