Computation of Kelvin chain retardation spectra of aging concrete

Zdenek P Bazant*, Ali Asghari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


A method of computing the age-dependent spectra of a Kelvin chain model from given data on creep of concrete is presented, along with a full listing of a FORTRAN IV subroutine. The method is based on a Dirichlet series expansion of creep rate as a function of the duration of creep test at constant current time. The inverse retardation moduli are approximated as a Dirichlet series in concrete age and as a quintic polynomial in the logarithm of the retardation time. These approximations serve at the same time as a smoothing device. They also enable explicit expressions for creep functions. The retardation moduli are determined by the method of least-squares. Numerical examples demonstrate that the retardation spectra completely characterize concrete creep because the original creep function can be recovered from them with a negligible error. The retardation spectra provide a rate-type creep law, which is necessary for analyzing large structural systems.

Original languageEnglish (US)
Pages (from-to)797-806
Number of pages10
JournalCement and Concrete Research
Issue number5
StatePublished - Jan 1 1974

ASJC Scopus subject areas

  • Building and Construction
  • Materials Science(all)


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