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<p>Understanding the time-dependent deformation behavior of concrete under mild thermal conditions is critical for ensuring the long-term performance of underground structures. This study proposes a novel three-dimensional fractional-order creep model that accounts for both viscoelastic and viscoplastic deformation mechanisms while incorporating thermal effects. The model leverages the advantages of fractional calculus to capture the multiscale and memory-dependent characteristics of concrete. It is extended from a one-dimensional to a three-dimensional form through stress–strain tensor decomposition and the integration of Perzyna’s viscoplastic flow theory. The parameter analysis is conducted to link the parameter values with concrete microstructure. A series of triaxial stepwise loading creep tests were conducted on C30 concrete specimens at temperatures ranging from 25 to 100&#xa0;°C under a constant confining pressure. The experimental data were used to calibrate and validate the model via parameter identification using the least-squares method. The model demonstrates strong agreement with experimental data across various temperature and stress conditions, accurately reproducing transient, steady-state, and accelerating creep phases. Furthermore, temperature-dependent expressions for the elastic shear modulus, viscoelastic modulus, and viscoplastic viscosity were established, enabling the prediction of concrete creep behavior under different thermal environments. The proposed model provides a robust theoretical basis and practical guidance for the long-term durability design of concrete support systems in mild-temperature underground engineering applications.</p>

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A three-dimensional fractional creep model for concrete: insights into creep behavior under mild thermal conditions

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • Teng Su,
  • Chuang Ge,
  • Xiaotian Hu,
  • Jiawei Li,
  • Zelin Liu

摘要

Understanding the time-dependent deformation behavior of concrete under mild thermal conditions is critical for ensuring the long-term performance of underground structures. This study proposes a novel three-dimensional fractional-order creep model that accounts for both viscoelastic and viscoplastic deformation mechanisms while incorporating thermal effects. The model leverages the advantages of fractional calculus to capture the multiscale and memory-dependent characteristics of concrete. It is extended from a one-dimensional to a three-dimensional form through stress–strain tensor decomposition and the integration of Perzyna’s viscoplastic flow theory. The parameter analysis is conducted to link the parameter values with concrete microstructure. A series of triaxial stepwise loading creep tests were conducted on C30 concrete specimens at temperatures ranging from 25 to 100 °C under a constant confining pressure. The experimental data were used to calibrate and validate the model via parameter identification using the least-squares method. The model demonstrates strong agreement with experimental data across various temperature and stress conditions, accurately reproducing transient, steady-state, and accelerating creep phases. Furthermore, temperature-dependent expressions for the elastic shear modulus, viscoelastic modulus, and viscoplastic viscosity were established, enabling the prediction of concrete creep behavior under different thermal environments. The proposed model provides a robust theoretical basis and practical guidance for the long-term durability design of concrete support systems in mild-temperature underground engineering applications.