3.1.5.16. Creep Material – Wrapper Creep Material

This command is used to construct a uniaxial time-dependent material object that wraps around a given base material to simulate both creep and shrinkage under sustained loads. The creep and shrinkage are modeled following the guidelines of ACI 209R-92.

uniaxialMaterial Creep $matTag $baseMaterial $tD $epsshu $psish $Tcr $phiu $psicr1 $psicr2 $tcast

Argument	Type	Description
$matTag	integer	Integer tag identifying material.
$baseMaterial	integer	Integer tag identifying base material.
$tD	float	Analysis time at initiation of drying (in days).
$epsshu	float	Ultimate shrinkage strain denoted as \((ϵ_{sh})_u\) in Eq. 2-7 of ACI 209R-92.
$psish	float	Fitting parameter of the shrinkage time evolution function denoted as \(f\) in Eq. 2-7 of ACI 209R-92.
$Tcr	float	Creep model age (in days) used for the calculation of $phiu.
$phiu	float	Ultimate creep coefficient defined as the ratio of creep strain to initial strain, denoted as \(ν_u\) in Eq. 2-6 of ACI 209R-92.
$psicr1	float	Fitting parameter of the creep time evolution function denoted as \(ψ\) in Eq. 2-6 of ACI 209R-92.
$psicr2	float	Fitting parameter of the creep time evolution function denoted as \(d\) in Eq. 2-6 of ACI 209R-92.
$tcast	float	Analysis time corresponding to concrete casting (in days).

Note

1. Shrinkage concrete parameters should be input as negative values (if input as positive, they will be converted to negative internally).

References

This wrapper creep material was adapted from the TDConcrete material by Michael Scott. The TDConcrete material was developed by A. M. Knaack and Y. C. Kurama. A manual describing the use of the TDConcrete concrete model can be found at: https://data.mendeley.com/datasets/z4gxnhchky/5

Detailed descriptions of the model and its implementation can be found in the following:

1. American Concrete Institute (ACI). (2002). ACI PRC-209-92: Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures (Reapproved 2008). ACI Committee 209. ISBN: 9780870311222.

2. Knaack, A. M., & Kurama, Y. C. (2018). Modeling Time-Dependent Deformations: Application for Reinforced Concrete Beams with Recycled Concrete Aggregates. ACI Structural Journal, 115(1).

3. Knaack, A. (2013). Sustainable concrete structures using recycled concrete aggregate: Short-term and long-term behavior considering material variability (Doctoral dissertation, University of Notre Dame), 680 pp.