A precise internal-stress calculation algorithm for the evolution of cracking risk of the steam-curing box girder

•The refined numerical model considers the temporal-spatial evolutionary difference.•The algorithm is established to reveal the thermal behavior of box girder.•The thermal stress evolution processes are monitored by the field test.•The results of numerical simulation and field tests are compared.•Parametric analysis is performed to investigate the influence of key factors. Thermal cracking caused by the combination of heat liberation and thermal boundaries becomes a more and more serious problem during the entire steam-curing process. To understand the rules of cracking risk and find the key factors determining the distribution of thermal stress, the numerical simulation algorithm is established and the verification field tests are deployed. Firstly, based on the equivalent maturity concept, a refined mathematic model of the thermo–mechanical coupling field is established, which fully considers the temporal-spatial evolutionary difference of material properties and hydration heat release. Secondly, the numerical algorithm is further set up for the evolution law of the thermal stress and cracking risk based on the finite element method. Thirdly, triaxial temperature strains of key points are monitored using Fiber Bragg Grating (FBG) sensors in the field. Effectiveness and accuracy of the model are verified by the agreement between numerical simulation and experimental results. Finally, based on the verified numerical model, parametric analysis is performed to investigate the influence of various key factors affecting the distribution law of the thermal stress field and the evolution law of the cracking risk. The results show that the curing temperature (Th) and parameters of the hydration exothermic model (θu and m) are crucial to influencing the thermal behavior of the steam-curing box girder. The research provides a refined numerical algorithm of the thermo-mechanical coupling field and contributes to the high quality of huge box-girder during the entire steam-curing process.