Which one of the following is the creep co-efficient at any time ? (Where Cct is the creep co-efficient at any time and Ccu is the ultimate creep co-efficient and t is the time in days after loading)
- ACct = t0.60 / (10 + t0.60) · CcuCorrect
- BCct = t0.50 / (10 + t0.50) · Ccu
- CCct = t0.40 / (10 + t0.40) · Ccu
- DCct = t0.70 / (10 + t0.70) · Ccu
Solution
Concept
Time function of creep (ACI 209)
Formula
Ct = t0.6 / (10 + t0.6) · Cu
Step-by-step solution
1. The ACI 209 creep time function is t0.60 / (10 + t0.60).
Explanation
Creep develops with time, approaching its ultimate value asymptotically. The exponent 0.60 is the ACI standard.
Why the other options are wrong
The other exponents (0.4, 0.5, 0.7) are not the ACI exponent for creep.
Shortcut
Creep: t0.6/(10 + t0.6); shrinkage: t/(35 + t).
Correct answer: A) Cct = t^0.60 / (10 + t^0.60) · Ccu