Those are "gussets". Done right and they help with stiffness considerably. Done wrong and they form a place to start a fatigue crack - look at a can-opener that makes a triangular opening - the tip of the opener piercing the can is similar to what a badly located gusset can do if there are enough loading cycles.

I would just call it bent stiffener plate, or squaring plate.

"Gussets" or "gusset plates". Commonly used on things that aren't analyzed.
To analyze the gusset itself, I treat it as if divided into strips along the free edge, and use column equations to find the allowable strength of each strip. Then make the assumption that one strip can't buckle unless the whole thing does, so sum or integrate the resulting strengths to find total vertical load or total moment load that can be applied to the gusset. There should be potential for a nice master's thesis in those things.

I don't find the strips that problematic and use an approach similar to JStephen... generally average outer edge and middle strip... biggest concern I have is what 3DDave noted about the effect on the member it is attached to... I go through hoops sometimes in convincing others that it's generally less costly to use a thicker base plate than to use gussets, in particular with HSS items.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

SoiloftheMonth,

It would be good to change your thread title, as you are not asking about "movement", but rather about moment. Also in the first sentence. Two very different things.

Agree on gussets. That’s what we call them in Australia.

We would call then stiffener plates or buttress plates. We've seen the fatigue issues noted above when these are used at connections of poles to base plates. They seem to cause more problems than they solve in those applications.

Rod Smith, P.E., The artist formerly known as HotRod10

Quote (They seem to cause more problems than they solve in those applications.)

That's why I like thicker baseplates... best of both worlds... I wish engineers would do this.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Thicker base plates can be a good option, but in the OP's application, there are no base plates. Agree with others that he has shown gussets, also called stiffeners.

Yup... was in reference to Bridgesmith's comment... sorry... still like thicker baseplates.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Don't make the gussets too stiff, they are just supposed to add a little.
If they are too stiff then you will get buckling and/or cracking at the ends.
And remember to notch the inside enough to clear the inside weld so that you have overlapping welds.

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P.E. Metallurgy, consulting work welcomed

Appreciate it @dik @EdStainless @hokie66 @BridgeSmith @Tomfh @JStephen @r13 @3DDave. Fixed moment spelling, good check @hokie66.

SOM

Not trying to be too picky or anything, but the weld on the left picture would not pass any kind of inspection in my corner of the world.

The detail on the right uses square HSS; triangular sections of HSS would strengthen moment better than a single gusset plate.

BA

Mitred knee joints can be used for CHS or RHS sections (see detail and link below).
See sketch below for unstiffened and stiffened details.



https://steeltubeinstitute.org/resources/hss-knee-...

BA