Hi,
I've encountered a scenario in prestressing design where with the decreasing of total number of strands, the Mu provided somehow increases. Attached are two screenshots with different total number of strands & corresponding Mu.
-Total number of strands = 63, Mu = 13947,8
-Total number of strands = 59, Mu = 14852.7
Does anyone has any idea what is the design calculations behind this?
My software version is: LEAPBridgeConcrete Version 19.02.00.33, I've also attached this LEAP bridge file
.Thank you very much.
Is Leap capable of showing the prestressing force for each strand? maybe you might see lower prestressing force at the strand below the typical of ~0.75*fpu. My guess is adding more strands (in your case, more straight strand), it would certainly improve the tension check at the bottom fiber and probably the capacity, however your design might be at a point that adding more strand would make you compression check [ (0.45 or 0.6) * sqrt(f'c) ] to be violated, probably during release. Therefore, the software is reducing strand force in order to make the stresses check to pass.