[en] High temperature structures of LMR experience inelastic deformation such as plasticity and creep due to high temperature operating temperature of 530∼550 .deg. C. The generated creep strains are connected with the stress relaxations, redistributions and/or progressive deformations. The superposition of primary and secondary stresses may lead to enhanced creep deformations. The term 'creep ratchetting' refer to the phenomenon where enhanced creep occurs with plasticity ratcheting. The interchange of elastoplastic and creep strains is important for its understanding. Since creep ratcheting is highly nonlinear structural behavior, it is required to secure the proper analysis technique to evaluate inelastic strain due to enhanced creep. In this project, the simplified evaluation method for enhanced creep using core stress concept was investigated and the enhanced creep of pipe subjected to sustained axial tensile loading and transient thermal loading with hold time was evaluated using several analysis models; that is, isotropic hardening model, kinematic hardening model and combined hardening model with Norton's power law creep equation. In addition, the viscoplastic analysis using NONSTA-VP was performed for comparisons. The simplified evaluation method using core stress concept yields conservative result as expected. It is necessary to systematize the simplified evaluation procedure, to analyze the conservatism of the method, and to improve the inelastic analysis techniques including NONSTA-VP