Accurate approximations of concrete creep compliance functions based on continuous retardation spectra

• Approximations of continuous retardation spectra of a number of concrete creep models have been derived.
• Accuracy of the corresponding approximations of compliance function by Dirichlet series has been evaluated.
• The accuracy has been increased by adjustment of the discrete retardation times.

This paper presents a detailed analysis of the continuous retardation spectra corresponding to a number of concrete creep models stipulated by various codes and recommendations. Approximations of various orders based on the Post–Widder formula are constructed, and the accuracy of the corresponding Dirichlet series approximating the compliance function is assessed. It is shown that the accuracy can often be substantially increased by appropriate modifications of the discrete retardation times used by the Dirichlet series. Practical hints regarding the choice of the discrete retardation times and the order of integration used in the evaluation of the compliance coefficients are provided.