Friction and wobble

[ajk1]

Can anyone tell me what friction and wobble coefficients that they use for monostrand unbonded single strand post tensioning tendons in high density polythy;ene sheath? Please be clear whether you are using imperial or metric units. I am doing some rehab work on a 1977 garage where the beams were post tensioned using unbonded monostrand tendons (NOT bonded tendons in ducts). I expect that they used stress relieved strand (not low relax) at that time and that they stressed to 75% of G.U.T.S. There are friction and wobble cefficients in the PTI Manual but they give only ranges and never use the terminology "monostrand".

 

[rollerich]

Follow OSHA
load test to 1.25 times the required loading and verify deflection.
Then go backwards through your calcs and you will have your answer.
Mollerich@ats-sd.com 40 yrs PE

 

[ajk1]

to rolleric - This is an existing building. Anyway, since concrete deflection calculations are not very good at predicting the actual deflection (because small changes in magnitude of input variables produce large changes in calculated defelctions. For example, what effective flange width should be used for deflection calculations, etc.) I don't see how this could determine anything with the reliability that we are looking for. I am surprised that no one out there can suggest what friction and wobble coefficients were used in the past for monostrand systems in the "pull-though" type of plastic sheath.