Concrete Creep and Shrinkage: Shrinkage

Description

Defines the shrinkage component of concrete creep data.

Shrinkage data can be entered to specify the change in volumetric strain over time by referencing a Strain vs Time table or by using a standard shrinkage formula.

Unlike pre-strain attributes generally applicable to elements, a positive shrinkage applied through creep data causes a volumetric contraction (i.e., a shrinkage) in the material, whilst a negative shrinkage causes volumetric expansion (i.e., a swelling) in the material.

Shrinkage Data vs Time

Specifies a previously defined Strain vs Time table as the variation of volumetric (shrinkage) strain with time.

A positive value of strain in the table causes shrinkage, whilst a negative value of strain in the table causes swelling.

Shrinkage Formula

The formula is a hyperbolic expression. The implementation of this expression in Strand7 is in a generalised form, which makes it amenable to many commonly used concrete design codes such as ACI 209R-92 and CEB FIP Model Code 1990.

is time;

is the age of concrete at first loading;

is a time exponent;

is a parameter that influences the rate of development of shrinkage strain;

is a function exponent; and

is the ultimate shrinkage strain (or the limit value of shrinkage strain as time approaches infinity).