POST TENSIONING GROUT STRENGTH FOR TENDON THAT PASSING THROUGH COLUMN/WALL

[aimansuo]

Hi I'm from Malaysia and new to post tensioning.

I'm working with bonded systems flat slab with drop panel and the tendon arrangement mostly is banded/distributed type. So some tendon are required to go pass through column and shear wall. I'm looking for explanations whether the grout strength for tendons that are passing through column/shear wall shall be of the same strength/grade with columns/shear walls. I'm finding hard time finding this information. Does anyone knows where I can refer this? Fyi the slab concrete grade is 35mpa and the columns/shear walls is 40mpa.

Thanks.

 

[Retrograde]

With a strength difference of only 5MPa it won't be a problem.

More generally you should check the transmission of axial force through the floor if there is a large difference in strength grade between the column and the slab. This should be covered in your design Code.

 

[rapt]

Concrete grout strength is not really controllable. It is normally about 40MPa.

On another note, it is completely illogical to use banded/distributed with a flat slab and drop panels. It you are using the PTI full Panel Width design approach for this it is rubbish (as are a couple of Text Books and Manuals that suggest the approach)! You are grossly over estimating the capacity in the distributed direction.