Modeling concrete and polymer creep using fractional calculus

Although the strains on a given material depend on its properties and, in general, on the stresses, on the temperature and on the time under load, they may be modeled as a function of the stresses alone in most practical structural analyses at low service-to-fusion temperature ratios. Most metallic and ceramic alloys can be modeled in such a simplified way at room temperatures, but some important materials, among them polymers and concretes, can creep significantly even at room temperatures. Under relatively low stresses, they can usually be modeled as linear viscoelastic using simple rheological models based on springs and dashpots. However, in many practical cases such models cannot fit well experimental data unless many of those elements are used, a problem that can much impair their use in structural analyses. Fractional rheological elements based on fractional calculus techniques have been recently proposed as a promising modeling technique to avoid this problem, and in this work their performance is evaluated by comparing their fitting behavior with traditional modeling techniques, using representative creep data from polypropylene and from a medium strength concrete. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The strains on a given material can often be simplified as a function of stresses alone, depending on factors such as properties, stresses, temperature, and time under load. While most metallic and ceramic alloys can be modeled using linear viscoelastic models at room temperatures, some important materials like polymers and concretes may exhibit significant creep even at room temperatures.