Achieving pin connection in concrete by rebar extension 1

[hsn199]

Hey, by what value shall we embed the beam rebars into exterior columns, so that pin condition is achieved?
I've previously heard that it's (0.1-->0.15 * effective depth), is this true?

 

[hokie66]

Why do you want a pinned connection? It is unrealistic to try to provide a pinned connection in a reinforced concrete structure by controlling the length of reinforcement embedment. Now, if you are talking about analyzing a beam as pinned, just do it.

 

[chekre]

If u want to end your reinforcement by a hook, bottom reinforcement should extend beyong the center line of support and have still enough space to ensure the 4 x bar diameter if u are dealing with bars up to 25mm, otherwise, it is 5 x bar diameter.

 

[shin25]

As Hokie said, it may not be desirable to detail an exterior beam to column connection with no top reinforcing or very little development length to act as pinned connection. Following should be kept in mind when deciding on such detail:

1. Will the connection see any load reversal due to lateral load?
2. Has the minimum integrity reinforcement been provided to satisfy local building code?
3. Does the beam to column connection have sufficient strength in shear without much longitudinal reinforcing?

 

[JedClampett]

I usually justify the pinned analysis by comparing the relative stiffness of the column vs. the stiffness of the beam. Beams are typically twice as deep as the column depth or roughly four times as stiff. So even if the bars are developed, the moment transferred to the column is small. And as the others have said, end the column bars with hooks.

 

[TXStructural]

DO NOT TRY TO PIN REINFORCED CONCRETE CONNECTIONS.

The analysis of members is a notional design simplification that cannot be achieved by simply making the structure weak. ACI 318 and similar codes are based on continuous reinforcement, and you cannot discontinue reinforcement except as permitted in the code. All parts of 318 work together, and you cannot use the chapter of flexure and ignore the "details of reinforcement" chapter.

 

[WARose]

I wouldn’t do it unless you had to.

That being said, the last time I did a connection like that in reinforced concrete I had a note on the drawings to grease the bar (or use some sort of bond breaker) so that the only thing the bar could transfer is shear.

 

[hsn199]

Thanks all for your valuable replies. Let me make it more clear. Referring to the attached image below, shall I develop the reinforcements till the end of the wall?!!