New Concrete Beam to Existing Beam - Reinforcement Splice 1

[cgstrucg]

Hello,

I haven't done a lot of concrete design and have a very basic question. I have a new concrete beam that is framing into the existing beam and we used #5 bar with HILTI HY200 embedment depth 6" into the existing beam to develop that connection. Now something happened in the field and the contractor messed up that connection and I am evaluating to see if that bar can still work.

Please see the attached sketch. I have found the moment in that beam splice and also the tension that the bar is going to take. Now I want to check if that beam splice works or not. I have already checked that that bar with that much embedment is able to take that much tension and wanted to confirm if that's the only check I needed to do or is there any other check I am missing.

New slab thickness is 13" and the existing slab is 5". I found the moment at the break-in point considering a simple span beam.

Thanks
CG

 

[KootK]

I have a new concrete beam that is framing into the existing beam and we used #5 bar with HILTI HY200 embedment depth 6" into the existing beam to develop that connection.

I'm struggling to figure out the situation here. You mention two beams above but I only see one beam in your sketch. What am I missing?

 

[cgstrucg]

I am sorry if I phrased something wrong, That hatched area is the existing slab and the white area with rebars is the new slab? The existing slab sits on a cantilevered part of the new slab for only 1 ft. That #5 bar is the one which is connecting new slab and the existing one and that bar is spaced 18" O.C.

 

[KootK]

No worries, we'll get there. How accurately does this reflect your situation?

 

[cgstrucg]

I should have done something like this.

Please see attached sketch. I will try to put better pictures next time.

 

[cgstrucg]

From this sketch, that bar which is going into an existing slab from the new one has 6" embedment in existing slab and is #5 bar. In my original thread, I mentioned that I have calculated approx tension in that bar considering a simple span beam and that bar is good for the pullout. I have a feeling that that's not the only check which should be done to check if that beam splice connection works or not and am not sure what else to check.

 

[KootK]

Would you say that your fundamental structural model is this?

 

[cgstrucg]

Somewhat Yes. Instead, I assumed the left pin in the middle of that new beam as that 2'6" high concrete is sitting on a steel beam connected via studs. Another pin at the end of the right end of the existing slab.

This is what it became after the contractor messed up. So that's why that #5 bar (going from new to existing slab) would get really high moments for gravity load then what the senior engineers designed it for. Initial design had a counterweight to balance that extra load coming from the existing slab and contractors messed it.

Just realized from your posts I can share images like this

 

[Celt83]

If KootK's last sketch accurately represents your situation I'd look in the PCA manual at the design of the flange for inverted pre-cast T's for the checks and detailing of the bars for your "seat" slab supporting the existing slab.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[KootK]

For such a short span in the new slab, designed as a simple span, I'd really only consider the dowels as performing the function of tying the new and old diaphragms together for in plane forces. As such, demand would be pretty small and you should be okay here. I wouldn't attempt to make this any kind of true, flexural splice.

 

[r13]

I still don't get where the contractor has messed up verses the original design.