Precast Double Tee Connections

[KimWT]

Hi!

Some engineers want to put double tee to litewall connections at DT stems (Det-2)
while others put them in the middle between two stems (Det-1).
What effects do they expect from different locations?
Why don't they place embed plates at the stem like Det-2 where more concrete mass can be used?

Thanks for your comment in advance!

 

[KootK]

These are lateral/diaphragm connections rather than the connections that support the vertical TT reactions, right? If so, they can be placed most anywhere without seriously affecting performance. And the location between stems would give you great edge distances and minimal congestion.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KimWT]

KootK,

Thanks for your response!
I wonder horizontal edge distances of 5ft vs 2.5ft make a big difference.
Are they considered as a field?
I think a local failure around embed plate may be more critical.

Isn't there any other reason?

 

[KootK]

You're most welcome KimWT.

I wonder horizontal edge distances of 5ft vs 2.5ft make a big difference.

Surely not if they are lateral connections.

Are they considered as a field?

Not sure what you mean by this. They may well be considered as in the field for lateral connection purposes.

I think a local failure around embed plate may be more critical.

You're probably right.

Isn't there any other reason?

You mean besides:

1) If they are lateral only connections then there's really no reason for them to be at the stems and;
2) Congestion is probably reduced if the connections are not at the stems?

You've yet to answer this important questions of mine:

These are lateral/diaphragm connections rather than the connections that support the vertical TT reactions, right?

I can better answer your questions if you supply an answer to mine.






I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Teguci]

It's a minor issue, but when the DTs are loaded the bearing ends will rotate and compress the plastic bearing shims (korolath). I'd think what little additional flexibility there is at the centerline between stems (as opposed to directly over the stems) would add to the lifetime of the connection. Of course this is even more of a problem at the Inverted Tee to column connections where a more compressible bearing pad is used and the welded plate connection must be directly over the beam (countered by the IT beam being more rigid over a shorter span).