Axial Tension in a Post-Tensioned Member
Axial Tension in a Post-Tensioned Member
(OP)
Hi all,
I have a post-tensioned member that has an axial tension load in additon to the bending moment and shear. There is going to be no non-prestressed reinforcing in the member. How do I properly account for the additional stress in the strand and overall reduction in the allowable moment due to this tension? At this point the only thing I can think to do is to calculate the stress in the strand at the moment that I need and then add the additional stress from the tension load and see if it comes out less than or equal to fps. Does this sounds reasonable? Is there a better way?
I would really appreciate some insight into this.
Thanks,
waytsh
I have a post-tensioned member that has an axial tension load in additon to the bending moment and shear. There is going to be no non-prestressed reinforcing in the member. How do I properly account for the additional stress in the strand and overall reduction in the allowable moment due to this tension? At this point the only thing I can think to do is to calculate the stress in the strand at the moment that I need and then add the additional stress from the tension load and see if it comes out less than or equal to fps. Does this sounds reasonable? Is there a better way?
I would really appreciate some insight into this.
Thanks,
waytsh






RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
This is sort of the fundamental of prestressing. If you apply an external tension force, it is true that the strands have to resist that force. But at the same time, the force resisted by the strands is decreased by the same amount due to the compressive force on the concrete being reduced. So the strands don't know the difference.
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
It all depends if it is cracked.
The only way to work out what is happening is to do a strain compatibility cracked section analysis and work out the different strains and related stresses and come up with a tension in the tendons under that load condition.
You cannot just assume that the force will be absorbed by the concrete. Axial tension combined with bending need to be considered together along with cracking if the sectionion goes into tension and the resultying stresss condition determined.
RE: Axial Tension in a Post-Tensioned Member
Yes, we digressed from the OP, but by waytsh's second post, he is going to keep the entire section in compression.
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
RE: Axial Tension in a Post-Tensioned Member
I won't have any more comments in this thread.