Fc28 σp, fc’, design value of concrete compressive strength.
CF - Consistency parameter of the fresh concrete.
ZF - Cement hardening parameter.
PHI(t,t0) φ(t,t0) Creep coefficient variation with time.
EPS(t,t0) εcs(t,ts) Shrinkage coefficient variation with time.
RHO(t) ρ(t) Relaxation factor variation with time.
EMOD(t) Ec(t) E-Modulus variation with time.
Fc28
Design value of concrete compressive strength. This value is defined in most design codes as the compressive strength of a cylindrical probe at an age of 28 days. Some creep and shrinkage models us it, to determine the creep coefficient and the time de- pendent elastic modulus.
The parameter Fc28 is assigned internally to the intrinsic variable Fc28 to be used for further user defined variable definitions.
CF
The parameter CF characterises the consistency of the fresh concrete at casting time.
Three fresh concrete consistency groups are distinguished in accordance with EN V 206:
CF = 1 stiff (small water-cement ratio) CF = 2 plastic (medium water-cement ratio) CF = 3 semi-fluid (high water-cement ratio)
The parameter CF is assigned internally to the intrinsic variable CF to be used for fur- ther user defined variable definitions.
This parameter is used in several creep& shrinkage model codes to determine the creep or shrinkage coefficients, e.g. in the improved MC 78 shrinkage prediction model. In- termediate values are allowed to be entered, the related coefficients will then be deter- mined by interpolation procedures.
ZF
The cement hardening parameter ZF is also used for the determination of creep and shrinkage coefficients. It characterizes the type of cement used for the concrete. Three standard cement quality types are on the market:
ZF = 1 slowly hardening cement (SL)
ZF = 2 normal and rapid hardening cement (N, R) ZF = 3 rapid hardening high strength cement (RS)
The parameter ZF is assigned internally to the intrinsic variable ZF to be used for fur- ther user defined variable definitions.
This parameter is also used in several creep & shrinkage models for the determination of the creep and shrinkage coefficients. Intermediate values are allowed, resulting in interpolated related coefficients.
Note: The definition of CF and ZF is only required for creep & shrinkage models based on them.
They are not necessary, when user defined creep and shrinkage coefficients that do not de- pend on them are used (for further details chap. 7.4.4.1. “Material Parameters”).
WCR
The water-cement-ratio (WCR) is the ratio between the content of water and the content of cement in the fresh concrete. It defines the amount of water per 1 kg cement). This ratio governs essentially the quality of the concrete. The strength of the concrete in- creases with decreasing values of WCR (0.4-0.7).
CECO
CECO describes the content of cement in the concrete. It defines the amount of cement (weight) in the volume unit of the concrete (kN/m3 when default units are used).
PHI(t, t0,…)
Creep coefficient, describing the ratio between the creep strain and the appropriate elas- tic strain. The creep coefficient must be specified as a user defined variable, if creep and shrinkage should be considered in the analysis. Predefined variable sets covering stan- dard creep model codes (CEB MC 78, CEB MC 90, …), may be used, if the required parameters (Fc28, CF, ZF, RH, …) for evaluating the creep coefficient have been de- fined. The required data are described in detail in chap. 7.4, Creep & Shrinkage.
EPS(t, t0, …)
Shrinkage coefficient, describing the shrinkage/swelling strain within a certain time interval. The shrinkage coefficient must be specified as a user defined variable, if creep and shrinkage should be considered in the analysis. Predefined variable sets covering standard creep model codes (CEB MC 78, CEB MC 90, …), may be used, if the re-
RHO(t, t0)
Relaxation factor for the pre-stressing tendons as a function of the time interval. A user defined variable has to be defined if the relaxation of the pre-stressing steel should be taken into account.
This functionality is not yet implemented!
EMOD(t)
E-Modulus variation with time. A user defined variable may be defined, describing the time dependency of the elasticity modulus E-Modl of the structure. This might be a function related to the basic modulus via the intrinsic variable E28, or some other defi- nition (e.g. related to the design compressive strength as proposed in the CEB90 model code). Note that the time dependent modulus is not automatically used in the LOADS AND CONSTR. SCHEDULE analysis, but must be activated by the update function in "LOADS AND CONSTR. SCHEDULE #STAGE !ACTION.