Simple Support vs Moment- Thoughts

[ToadJones]

I am analyzing an existing connection.

Two beams frame into one another over top a column (sitting on column cap plate)
The beams each have a pair of clip angles that mate up and bolt together at the ends. Nothing ties the top/bottom flanges together.

Question is, for analysis, would consider this a moment connection or just shear? (even though the clips see no real shear force due to the beams resting on the column).
I realize that the connection is somewhere between pinned & fixed, but what is a more accurate assumption>?

I am leaning towards pinned since nothing ties the flanges together.

 

[paddingtongreen]

Unless the clips are very thick (>5/8"), it is pinned by definition. AISC relies on the flexibility of the thinner clips for distance make-up.

I'm curious, are the bottom flanges not connected to the cap plate?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[ToadJones]

Oh, yes, the bottom flanges are connected to the cap plate. I misspoke there.
I guess my thought was since the beams only experience positive bending, there is nothing tying the tension flanges together and if the clips are flexible (as you point out) it is a pinned connection.

 

[JAE]

Pinned.

 

[TXStructural]

Pinned. It sounds like a corner condition, but if not: Have you considered the likelihood that the tops of the beams will try to roll (a need to stiffeners, etc.)? What about extending one beam across the top, about 4-5 ft. into the next span and splicing with web plates?

I cannot think of a single project in which I designed a beam-to-beam connection on top of a column.

 

[ToadJones]

beams cannot roll.
Its a crane runway.
The clip angles sandwich a plate that is connected back to the upper shaft of the crane column.

In hindsight, my question was a rather stupid one.

 

[hokie66]

It is a crane runway, therefore it is pinned. My motto...always use simple spans for crane runways.

 

[ToadJones]

hokie-
Your are 100% correct...but, this is existing, so it's not my choice.

I cant tell you how many runways I have repaired or completely rebuilt due to the original designers using fixed connections (theoretical) and knee braces that cause fatigue failures....hence my ultra sensitivity to applying the right conditions to my analysis.
I will have to assume the above described connection has enough ductility to allow for proper beam end rotation on the runway.
BTW, this runway is in remarkably great shape...built in the 30's but it does include pesky knee braces.

thanks

 

[hokie66]

Yes, the problem is that the knee braces can pry the beams and fail the web because of the way the clips tie the webs together. But if it hasn't happened yet, it probably won't.

 

[ToadJones]

yea- from my experience, riveted connections of this type do okay....bolted ones fail almost invariably.