RC frame - terrace
RC frame - terrace
(OP)
I have to design a terrace that is 9 x 9,50 m. Slab is 200 mm. I have 2 questions for you guys and I hope for some help.
1.) There is no column in the middle of a slab (where two middle beams are crossed)so the dimension of beams are quite big. I made a quick calculation and I got 350/650 mm (I also checked deflections). I don't have a 'feeling' since I normally don't design beams with a span like this. Is this normal dimensions or should I expect more/less?
2). Columns are on spread footings. If I model columns as pinned at base I get pretty big forces in columns (moments), but in this case there are only axial forces acting on footings. But if I select fixed support at base, then I get huge footings since they have to take care of moments that are transfered from column to footing. I think I should model bases as pinned. Do you agree? Since in reality there will be some moment transfer, should I design footings bigger than calculated from axial force?
1.) There is no column in the middle of a slab (where two middle beams are crossed)so the dimension of beams are quite big. I made a quick calculation and I got 350/650 mm (I also checked deflections). I don't have a 'feeling' since I normally don't design beams with a span like this. Is this normal dimensions or should I expect more/less?
2). Columns are on spread footings. If I model columns as pinned at base I get pretty big forces in columns (moments), but in this case there are only axial forces acting on footings. But if I select fixed support at base, then I get huge footings since they have to take care of moments that are transfered from column to footing. I think I should model bases as pinned. Do you agree? Since in reality there will be some moment transfer, should I design footings bigger than calculated from axial force?






RE: RC frame - terrace
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.
RE: RC frame - terrace
As for design, I'd use the dead load moments for a fixed base column and use that unfactored moment at the base for factored DL+LL design.
Dik
RE: RC frame - terrace
A major factor there is what your subgrade looks like. A softer subgrade will rotate more and act more like the pinned base. Bedrock brings you closer to a fixed condition.
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The name is a long story -- just call me Lo.
RE: RC frame - terrace