Shrinkage and Creep Parameters
Description
This form enables the parameters used in the shrinkage and creep calculations to be defined. Refer to the field help for more detail.
Form Graphic
Field Help
Shrinkage Strain, εsh
Shrinkage strain is calculated according to A5.4.2.3.3 of AASHTO LRFD 9.
When set to User Defined, a value may be entered for the combined shrinkage strain in the adjacent field.
Creep Coefficient
Creep in the concrete has the effect of reducing the effective modular ratio. The creep coefficient is applied to the compressive strain caused by permanent loads in order to obtain the strain due to creep. This time-dependent parameter is evaluated using A5.4.2.3.2 of AASHTO LRFD 9.
Alternatively, when set to User Defined, a value may be entered in the adjacent field.
Age At End Of Curing
The age of the concrete at the end of the curing process should be entered here. This value is used for the maturity value of the concrete in the determination of shrinkage strain according to A5.4.2.3.3 of AASHTO LRFD 9. The default is 3 days.
Age At First Loading, ti
The age of the concrete when permanent load is first applied should be entered here. This value is used for the maturity value of the concrete in the determination of creep coefficient according to A5.4.2.3.2 of AASHTO LRFD 9. The default is 10 days.
Age Of Concrete
The age of the concrete for which shrinkage and creep effects are required.
Ambient Relative Humidity
This field is available if either the shrinkage strain or the creep coefficient are set to Calculated. Shrinkage and creep in the concrete depend on a number of factors, of which the relative humidity is a major component. The relative humidity entered here will be used as defined in AASHTO LRFD 9 A5.4.2.3.2 (for creep) and A5.4.2.3.3 (for shrinkage).
Suitable values of relative humidity may be obtained from local weather statistics or from Figure 5.4.2.3.3-1 for structures located in the US. The default value is 70%.
Early Exposure to Drying
This field is available if the shrinkage strain is set to Calculated. This field should be checked if the concrete is exposed to drying before five days of curing have elapsed. If it is checked the calculated shrinkage strain as determined in AASHTO LRFD 9 A5.4.2.3.3 will be increased by 20%.