Structural Concrete - Hassoun

38 Chapter 2 Properties of Reinforced Concrete
Table 2.16
Coefficient S as Function of Cement Type
Cement Type European Type U.S. Type S
Slow hardening SL II 0.38
Normal/rapid hardening R I 0.25
Rapid hardening high strength RS III 0.20
where S is the coefficient that depends on cement type and can be determined from Table 2.16.
√
⎧
f
⎪3,118,310 3 cm28
(in. − lb)
⎪
1450
E cm28
= ⎨ √
(2.62)
⎪ f
⎪21,500 3 cm28
(SI)
⎩ 10
Creep coefficient, φ(t, t 0 ), can be evaluated from the given equation:
where
φ 28 (t, t 0 )=φ 0 β c (t − t 0 ) (2.63)
φ 0 = notional creep coefficient
β c (t,t 0 ) = equation describing development of creep with time after loading
φ 0 = φ RH β(f cm28
)β(t 0 ) (2.64)
where φ RH is the relative humidity factor on the notional creep coefficient given by
⎧
⎪1 + 1 − H∕100
√ (in. − lb)
⎪ 0.46 3 he ∕4
φ RH = ⎨
⎪1 + 1 − √ H∕100 (SI)
⎪
⎩
0.46 3 he ∕100
ε as0 (f cm28
) is the concrete strength factor on the notional creep coefficient given by
⎧
⎪
⎪
β(f cm28
)= ⎨
⎪
⎪
⎩
5.3
√
f cm28
∕1450
5.3
√
f cm28
∕10
(in. − lb)
(SI)
(2.65)
(2.66)
β (t 0 ) is the age of concrete at loading factor on the notional creep coefficient given by
1
β(t 0 )=
(2.67)
0.1 + t 0.2
0
An equation describing development of creep with time after loading, β c (t, t 0 ), can be calculated
using the following equation:
( ) t − 0.3 t0
β c (t, t 0 )=
(2.68)
β H + t − t 0