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(3) The effect of elevated or reduced temperatures within the range 0-80 °C on the maturity of concrete may be taken into account by adjusting the concrete age according to Equation (A1.10):

where tT = temperature adjusted concrete age which replaces t in the corresponding equations; T(Ati) = temperature in °C during the time period Ati; Ati = number of days where a temperature T prevails.

The mean coefficient of variation of the above predicted creep data, deduced from a computerized data bank of laboratory test results, is of the order of 20 %.

(4) The values of 0(t,to) given above should be associated with the tangent modulus Ec(28) = 1.05 Ecm

When a less accurate estimate is considered satisfactory, the values given in Table 3.3 of 3.1.2.5.5 may be adopted for creep of concrete at 70 years.

A1.1.3 Shrinkage

(1) The shrinkage or swelling strains may be calculated from:

where

(cso notional shrinkage coefficient (Equation A1.12);

"s coefficient to describe the development of shrinkage with time (Equation A1.16); t age of concrete in days;

ts age of concrete in days at the beginning of shrinkage or swelling.

The notional shrinkage coefficient may be obtained from:

Ss(fcm) = [160 + pSc • (90 - fcm)] ' 10-6 (A1.13) where

"rh is given by Equation (A1.14)

(s (fcm) a factor to allow for the effect of concrete strength on shrinkage fcm mean compressive strength of concrete in N/mm2 at the age of 28 days "sc coefficient which depends on type of cement;

(4 for slowly hardening cements, S; "sc = (5 for normal or rapid hardening cements, N,R;

(8 for rapid hardening high strength cements, RS;

(- 1.55 • "sRH for 40 % r RH < 99 % (stored in air) "rh =( (A1.14)

where

"sRH is a coefficient to allow for the effect of relative humidity on the notional shrinkage coefficient, as defined in equation (A1.15).

where RH is the relative humidity of the ambient environment in % The coefficient for the development of shrinkage with time may be estimated from:

"s(t - ts) = [(t - ts)/(0.035.h02 + t - ts)]05 (A1.16)

where ho is the notional size in mm (Equation (A1.6) and (t — ts) is the actual non-adjusted duration of shrinkage or swelling in days.

The mean coefficient of variation of the above predicted shrinkage data deduced from a computerized data bank of laboratory test results is of the order of 35 %.

(2) Where a less accurate estimate is considered satisfactory, the values given in Table 3.4 of 3.1.2.5.5 may be adopted.

A1.2 Additional design procedures

(1) When the influence of the time-dependent deformation of concrete is considered to be of particular significance so that its evaluation requires the use of advanced calculation procedures (e.g. in the presence of elastic restraints; where variable imposed deformations occur; in allowing for the presence of symmetrical or assymmetrical reinforcement; for composite concrete or steel construction; etc.) reference should be made to appropriate specialist literature, in complying with P(1), P(2) and (5) of 2.5.5. In performing such calculations, the accuracy implicit in A1.1.2(3) and A1.1.3(1) should be borne in mind. A knowledge of environmental history, and of material composition and properties, is important for accurate predictions.

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