A novel hydro-elastoplastic damage constitutive model for local failure prediction of RC beams under contact explosion

When buildings are subjected to extreme dynamic loads such as explosions or ballistic impacts, determining the local damage and overall dynamic response of reinforced concrete (RC) components is crucial for assessing the damage and overall stability of the structure. Numerical simulation, as an important method for predicting the local damage of RC components, relies on the accuracy of the material models. For concrete, a typical strain-softening material, the localization of deformation during finite element nonlinear analysis can lead to non-physical mesh size dependency, as seen in concrete dynamic models such as KCC, HJC, RHT, CSC, and Kong-Fang. Moreover, these models fail to account for the degradation of material stiffness, that is, cannot accurately predict changes in material wave impedance, and thus cannot describe the propagation of stress waves within the components. Although the previously proposed Yan-Chen2.0 model (Int J Impact Eng, 198(2025):105226) has addressed these issues and provided a detailed modeling process, it has not conducted quantitative verification of stiffness degradation and mesh size independence. Moreover, it lacks an evaluation of its applicability in predicting the local damage degree of RC beams under contact explosion. Based on the Yan-Chen2.0 model, this paper first reviews the modeling strategy. Then, it uses uniaxial compression (UUC) and uniaxial tension (UUT) numerical tests with different mesh sizes, as well as single-element numerical tests under three loading schemes: cyclic hydrostatic compression, cyclic uniaxial tension and compression, and tension-compression cycling. These tests are combined with the five aforementioned concrete models to quantitatively analyze the applicability of the Yan-Chen2.0 model. Finally, using the contact explosion tests on RC beams, the mesh size dependency of the predicted local failure modes by the six models was analyzed and compared. The results show that the Yan-Chen2.0 model can effectively reduce mesh size dependency in UUC and UUT; it can capture stiffness degradation during unloading under cyclic loading, with the strain-softening segment basically matching the experimental results. Under RC beam contact explosion, it has the lowest mesh size dependency in predicting local failure modes and dynamic responses, and can reveal the failure mechanism of RC beams under stress wave action. This study provides a reference for the selection of material models in numerically predicting local failure of RC components.