EUROCODE 2 WORKED EXAMPLES - Federbeton

EC2 – worked examples 6-48
Table of Content
h = (2Ac / u) = 1217 mm notional size of member;
Ac = 17.43×10 6 mm 2 gross section of the beam;
u = 28640 mm perimeter of the member in contact with the atmosphere;
φ (t∞,t0) : creep coefficient at time t∞ calculated from:
φ (t∞,t0) = φ0 ×�βc (t∞ - t0) = 1.5708 where:
φo = φRH × β( fcm) × β(t0) = 1.598 with
1 100
φRH = 1
013 + − RH
= 1.281;
. h
β( fcm) =
β(t0) =
53 .
fcm fcmo
1
. + t
02 .
01 0
⎛ t∞−t0 βc (t∞ - t0) = ⎜
⎝ β + t −t
H
∞
= 2.556;
= 0.488
0
⎞
⎟
⎠
βH = . ( . )
03 .
18
[ ]
= 0.983 with
1 5 1 + 0 012 RH h + 250 = 2155 > 1500 → 1500
If the improved prediction model of chapter 3 is used, the following values
for εcs (t∞ , t0) and for φ(t∞ , t0) may be evaluated:
ε cs (t∞ , t0) = 182.62 × 10 -6 ; φ (t∞ , t0) = 1.5754
in good aggrement with the previous one, at least for creep value.
Δσpr : loss of prestressing due to relaxation of steel calculated for a reduced initial
tensile stress of σp = σpgo � 0.3 Δσp,c+s+r (where σpgo is the effective initial
stress in tendons due to dead load and prestressing) and evaluated as
percentage by the following formula:
019 .
t
ρt =
⎛
ρ1000h ⎜
⎞
⎟ = ρ1000h × 3 where
⎝1000⎠
ρt = is the relaxation after t hours; for t > 50 years ρt. = ρ1000h × 3;
ρ1000h = is the relaxation after 1000 hours evaluated from Fig. 6.38;