anchoring to concrete

[YOO1]

I am designing post-tension anchor system to repair a dam. I am planning to use the “DYWIDAG post-tension system using bars”
This is with a bar length of 40’ to 50' and will be anchored to concrete with approximately 110kips applied load on the rebar. My intention is to use cement grout. To determine my bond length I need to know the working bond stress in the interface between the concrete (assuming 3000psi) and the bonding material (high strength grout). Could you please provide me with this info. or catalog. And any other suggestions or comments are welcomed. the idea is the same as rock anchors.

Thanks a lot

 

[PEinc]

Get a copy of the Post-Tensioning Institute's Recommendations for Prestressed Rock and Soil Anchors.

 

[PEinc]

http://post-tensioning.org/category/x_YY2lk4PT/Ground Anchors

 

[YOO1]

Thanks PEinc.

But the book does not give me the working bond stress in the interface between the concrete (assuming 3000psi) and the bonding material (high strength grout). It gives you the bonding to rock.

 

[PEinc]

Concrete should have better bond than many of the rock bonds listed. Also, the bonding of the small diameter bar to the grout will probably be more critical than the bonding of the grout to the larger diameter concrete drill hole. Concrete is mostly sand and hard, coarse aggregate. Look at the bond stresses for sandstone and hard limestone. Pick a lower bond stress and it probably will still not control your design.

Usually, anchors are long with plenty of bond length (maybe 10' in rock up to about 50' in some soils. If you are trying to design a very short bond length, you may be heading in the wrong direction.