Abstract: As a time-dependent property of concrete material, creep imposes significant influence on the stress of early age concrete. However, it is difficult in engineering to calculate the creep stress by using common available finite element programs. In view of this, through further development of the ANSYS user subroutine usermat, a userdefined material model was developed to introduce the implicit solution to the concrete creep equation. With the largest error lower than 0.3 MPa, the user subroutine usermat was verified through calculation examples and was applied to engineering. The results of the implicit concrete creep equation are in good agreement with measured values, and their variation trends are the same. The user subroutine usermat can be applied to engineering to predict and calculate the thermal creep stress of early age concrete.

Key words: thermal stress field, earlyage concrete, creep, further development of ANSYS, implicit solution