post-tension query

[malindu87]

When post tension is done usually the top surface is getting uneven (curved) due to small deflections. How to achieve an even surface in that case?

I there any standard methods to achieve this?

When post tension is done usually the top surface is getting uneven (curved) due to small deflections. How to achieve an even surface in that case?

 

[Ingenuity]

If I understand your term "uneven (curved)" correctly, you are referring to precamber or uplift deflections that are caused by the eccentricity of prestress from the section centroid and is usually a desired result that counteracts the final in-service deflections.

If you placed prestressing (pre-tensioned or post-tensioned) where the resulting prestress was concentric to the centroid you would only have axial shortening with no uneven or curved surfaces...but not a very efficient use of prestress.

For post-tensioning concrete design, you would avoid uplift by 'balancing' LESS than the applied permanent dead load (usually self weight).

 

[rconner]

[apply load (weight)?]

 

[racookpe1978]

How big are these deflections in the top surface? Inches/mm high and inches/mm long?
How many are deflections are present?
Why are you worried about them? What is your acceptance criteria for upper surface deflections, and why is that criteria set?
(Visual effect only? Flat steel plate needs to be mounted? Load type or load point supports?)