Concrete Wall - Minimum Reinforcement 3

[SkiisAndBikes]

Hello,

I have a project to design a 75ft. long, 12" thick curved wall for a cenotaph in Canada. Crack control is essential as no joints allowed and it will be an exposed, polished concrete surface. I have had a little experience with water retaining structures where minimum reinforcement ratio may be as high as 0.004, to reduce the chance of cracking. Very rough sketch attached. I would love to hear from any recommendations related to minimum reinforcement ratio for the horizontal reinforcement.

SkiisandBikes

 

[hokie66]

Thanks for that reference, BA. You have made me scratch head and reconsider. Although in some of the shapes shown, it would be impossible to keep the strands exactly centred all the way around, in a circular arc it could work. As well, when you think about it, this thing when post-tensioned would work as a classic circular arch, so bending would be negligible.

SkiisAndBikes,
Removing base restraint is the way prestressed concrete water tanks are built. I think they generally use rubber bearings, and there is no structural connection of the walls to the base slab.

 

[Zambo]

I've been using this topic to try to understand the theory of deflection due to post-tensioning. What I know is that if you have a series of box beams in a multi-span structure when you come to a curved section the beams will still have an upward deflection when stressed but there will be negligible deflection in plan.

So I withdraw the brake cable and end anchorage angle theories. But I'm pleased to see the link provided by BA. In the curved beam scenario the upward deflection is caused by the design of the tendon profile to prestress the beam to resist the moment caused by dead and live load. However in plan the tendon layout causes an axial compression and no horizontal deflection.

Is that right? Anyway it looks as if prestressing isn't under consideration.

 

[BAretired]

zambo,
You stated

However in plan the tendon layout causes an axial compression and no horizontal deflection.

I think it would be more correct to say that the tendons cause an axial compression and no bending. They do cause a slight horizontal deflection because the radius shrinks slightly under the compression.


BA