Curved Concrete beam tendencies

[Eldorado]

Gentlemen, I am working on a round building with a circular perimeter beam (68' building diameter). I am concerned that if I specify curved reinforcing bars that the steel will want to "straighten out" under gravity loads.

I have modeled the structure in STAAD using two (2) differing layouts.

In the first layout, I use straight beams from column to columns and apply my edge loads to the beam with an appropriate eccentricity to generate the equivalent torsion. In most, but not all cases, the actual construction can use straight reinforcement with the additional concrete needed for the radial shape being scabbed onto the straight beam.

In the second model, I still use straight beams, but have multiple segments between columns to more closely match the radius of the structure. I consider this to be a model for curved longitudinal reinforcement.

Both models appear to give close and reasonable results, but I wanted to ask if anyone has any information or suggestions that would apply.

Thanks.

 

[csd72]

Closed shear ties will hold the bars in. If you put them close enough the bars will be near enough to a straight line.

 

[ron9876]

Don't forget torsion. Make sure stresses work at all areas.

 

[civilperson]

67 degrees of arc for a forty foot long reinforcing bar could easily be hand formed with stakes and ties if you specify #4 or #5 bars. Any fab shop can bend larger bars to this radius bend if you insist on #8 up to #11. Field or shop bends are "permanent". Concrete is not the most efficient material since dome forces will put the hoop beam in permanent tension, I suggest you use rolled W shapes in 90 degree arcs at 53.4' lengths, (bent the easy way), with shear tab connectors between the webs and plates on the flanges.