RC frame for supporting roof structure 1

[n3jc]

Helo. Im dealing with a RC frame that supports wooden roof beams.

Im wondering about a model.

I have model 1: supports are modeled as pinned because there will be some rotation and its more conservative than fixed support model- larger bending moments in elements of RC frame

This RC frame is anchored in the concrete slab (bearing masonry wall under it). Im wondering if there is a need to model this RC frame with TENSION TIE as shown in the attached picture? We get axial tension force in a tie. So is there a need to calculate suffiecient reinforcement based on that force and place it in the concrete slab between both columns of RC frame?

Regards.

 

[KootK]

Yes, you'll need a tie element in order to justify the pinned supports. Otherwise, you'd have to use pin / roller which wouldn't make sense here as the implied movement would be destructive. Regarding the tie:

1) ACI prohibits the use of lap slices for such ties. Go mechanical slices or welded.

2) when designing the rebar, consider stiffness of the tie as well as the tension strength required. Significant tie elongation will cause problems and invalidate your design assumptions.

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.

 

[n3jc]

great post! tnx as always!

 

[n3jc]

One more thing - what if I get very small tension force in tension tie. lets say under 15 kN?
The suffiecient rebar is then less than As = 0,50 cm2... I think reinforcement in slab itself is sufficient for such a small force if colums of RC frame are anchored correctly in it...

 

[KootK]

I agree. And thanks for the kind words.

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.