Pinned vs Fixed Connections in Practise 4

[structuree]

I'm trying to get my head around how pinned vs fixed connections appear in practise. I'm struggling to identify whether a connection will result in an induced moment. It doesn't always seem as straightforward in practise as it does in theory.

For example, I am aware that typically a connection with 2 x bolts would be designed as pinned, and you wouldn't consider it as taking any moment, but you add 4 or 6 bolts, and you're probably trying to crank moment into the connection. Where is the line drawn?

 

[BridgeSmith]

When I have a connection that is not essentially pinned, I check the reactions on the structure assuming a fixed connection. If nothing is overstressed, I move on. If not, it's time to 'sharpen the pencil' and do a more refined analysis using a more realistic approximation of the rigidity of the connection. In 20+ years of bridge design, it's happened very rarely.

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

 

[StrEng007]

BAretired,
Let me clarify, the scenario I'm talking about is a single beam fixed at A and propped at B with a roller.

 

[BAretired]

Let me clarify, the scenario I'm talking about is a single beam fixed at A and propped at B with a roller.

The structure below has one degree of indeterminacy.
Using the slope-deflection equation, clockwise positive,

Ma = FEMab + UMb/2
where FEMab = Fixed End Moment[A-B] and UMb = Unbalanced Moment @ B (i.e. FEMbc - FEMba)

BA

 

[StrEng007]

BARetired,
Thank you. I use the force compatibility method and solve these with displacements. My original question was about whether or not you know of any beam formulas, similar to those found design manuals, that quickly solved these types of beam reactions for various loading patterns. I’ve noticed that most manuals don’t cover this particular cantilever with one propped end and overhang.

 

[BAretired]

Sorry, but I don't know of any formulas or manuals covering this particular case.

Remove Support B, calculate deflection at B from applied load, then determine reaction at B to produce the same deflection.