Title: A sectional approach for the bending creep of FRC based on uniaxial tension creep tests
Author(s): Vrijdaghs, R.; Di Prisco, M.; Vandewalle, L.
Publication: Symposium Paper
Appears on pages(s): 20-29
Keywords: Sectional analysis, creep of FRC, polymeric FRC, tensile and bending creep
The creep behavior of FRC elements remains an important obstacle to use FRC in structural
applications. Owing to the residual post-cracking strength properties of FRC, creep
deformations play an important role in the cracked sections and influence durability and SLS
requirements of structural elements. Therefore, it is of high importance to take creep
deformations into account in the design phase.
In this paper, the results of an experimental campaign involving both bending tests and
uniaxial tensile creep tests on polymeric FRC are presented. In the bending tests, a notched
FRC beam is subjected to loading-unloading cycles while the deformations over the cracked
section were recorded. The uniaxial tensile creep tests were performed on precracked FRC
samples to quantify time-dependent crack growth.
The bending behavior of FRC can be accurately predicted by the uniaxial constitutive model
of Model Code 2010 in the loading phase assuming a plane section approach. For the unloading
phases, a bilinear deformation distribution is assumed and a scalar damage evolution function
is fitted by an inverse analysis algorithm. The results of the sectional analysis compared
favorably with the experimentally observed data.
Finally, a sectional analysis approach is developed and presented in which bending creep
deformations are calculated using the uniaxial creep compliances. The initial stress and
deformation distribution in the cracked section is predicted by the inverse analysis. The results
show that the bending creep deformations of FRC can be quite large, and creep coefficients as
high at 7 are observed within 120 days. However, it should be noted that the creep algorithm
does not (yet) take into account additional cracking in time, and as such, the predicted creep
deformations are a lower limit of what can be expected in reality. More research is needed to
upgrade the algorithm to allow predictions including the time-dependent cracking behavior.