Practically, is it possible that the tensile forces generated in prestressing steel due to loading exceeds effective prestressing tensile force?
Typically, prestressing will range from 40% to 60% of the steel's nominal yield stress, depending on method, presence of bonding to concrete and code provisions. Activation of dead load due to prestressing camber and additional service loads will certainly increase steel stress (for bonded tendons). If the question is whether this increment alone due to permanent and service loads could exceed initial prestressing stresses, then that would bring prestressing steel around the yield point under service loads, which probably means that something has gone wrong in the design.
Dear Dr. Georgios Baltzopoulos
Thankyou very for kind explanations,
What I meant by loads is all of dead, super-imposed ans live loads, i.e all service loads.
If the prestressing is within the range of 40-60% of proof stress and the tensile stresses exceeds 60% and let us say 70% of (fy), practically such case occurs? and is their any risk? regardless to the design weather its wrong or not.
Typically, codes provide limits for both initial prestressing stress and under long-term service loading, so both should be satisfied. Generally speaking, high stresses in the prestressing steel under long-term service load combinations will mean more mild reinforcement required to satisfy ultimate limit state and possibility of excessive crack widths that expose the element to corrosion of the reinforcement.
So its durability and serviceability issue rather than strength limits.
Thankyou very much
Nice answer from Georgios Baltzopoulos .....
Actually, need to know the best answer might you trust...
Regards
Dear Dr Hussam,
Thank you for participating this discussion.
In practice, prestressing force are limited to a value according to applied code and exceeding this values under service loads will leads to developments of cracks and hence deterioration/corrosion of reinforcement. Any way, such case of loading should be avoided.
Dear Ali A. Abdulhameed ........ So well definition and answer you show.. Thanks for your sharing ... Please share me any new update...
Best Regards..
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