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<p>The ANSYS finite element program has been frequently used for thermal stress analysis of concrete. In ANSYS, the material properties of concrete are generally defined as fixed values or vary according to time or temperature histories. However, early-age concrete properties are highly sensitive to changes in time, temperature, and location, which should not be ignored. This research outlines a method to evaluate early-age thermal stress in concrete and details the integration of an improved USERMAT subroutine in ANSYS software. The subroutine utilizes a double exponential function to accurately model the hydration characteristics of concrete mixtures. For thermal analysis, the heat generation rate, and thermal material properties of concrete were modeled using equations based on the degree of hydration (DOH). These DOH-dependent equations allow the properties to change for each element based on the temperature, location, and time. For stress analysis, compressive strength, elastic modulus, and creep properties were established as DOH-dependent functions and incorporated into USERMAT. The tensile creep calculation in USERMAT under loading and unloading was verified using a long prism specimen. Concrete batches containing supplementary cementitious materials (SCMs) were delivered by ready-mix trucks to perform experiments validating the subroutine. Results show that the proposed method can effectively predict the strain peaks measured by vibrating-wire strain gages with a maximum error of about 4% and accurately predict the time of stress peak. The thermal stress analysis technique developed here can effectively evaluate the maximum early-age tensile stress to assess thermal stress in mass concrete and mitigate cracking risks.</p>

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Prediction of the early age thermal behavior of mass concrete containing SCMs using ANSYS, part 2: evaluation of thermally induced stresses

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Seyednavid Mardmomen,
  • Hung-Liang Roger Chen

摘要

The ANSYS finite element program has been frequently used for thermal stress analysis of concrete. In ANSYS, the material properties of concrete are generally defined as fixed values or vary according to time or temperature histories. However, early-age concrete properties are highly sensitive to changes in time, temperature, and location, which should not be ignored. This research outlines a method to evaluate early-age thermal stress in concrete and details the integration of an improved USERMAT subroutine in ANSYS software. The subroutine utilizes a double exponential function to accurately model the hydration characteristics of concrete mixtures. For thermal analysis, the heat generation rate, and thermal material properties of concrete were modeled using equations based on the degree of hydration (DOH). These DOH-dependent equations allow the properties to change for each element based on the temperature, location, and time. For stress analysis, compressive strength, elastic modulus, and creep properties were established as DOH-dependent functions and incorporated into USERMAT. The tensile creep calculation in USERMAT under loading and unloading was verified using a long prism specimen. Concrete batches containing supplementary cementitious materials (SCMs) were delivered by ready-mix trucks to perform experiments validating the subroutine. Results show that the proposed method can effectively predict the strain peaks measured by vibrating-wire strain gages with a maximum error of about 4% and accurately predict the time of stress peak. The thermal stress analysis technique developed here can effectively evaluate the maximum early-age tensile stress to assess thermal stress in mass concrete and mitigate cracking risks.