Endochronic Plasticity Theory-Based Dynamic Damage Constitutive Model Development of Concrete Materials

다국어 초록 (Multilingual Abstract)

Concrete is a typical rate-sensitive material, and the correct selection of the constitutive model is crucial for accurately predicting the elastic-plastic response of structures during earthquakes. The nonlinear characteristics of concrete are a result of the evolution, development and accumulation of microscopic damage, which traditional elastic-plastic constitutive models fail to adequately capture. While damage mechanics theory could describe the nonlinear behaviorof concrete due to the gradual expansion of internal micro-cracks, a single theoretical model cannot fully explain the mechanisms and characteristics of the multi-axis nonlinear behavior of concrete. This study aims to introduce the endochronic plasticity theory to depict the softening effect of concrete material, thereby eliminating the concept of yield surface in traditional elastic-plastic models and better aligning with concrete’s deformation characteristics, simplifying the nonlinear calculation process. Additionally, in conjunction with damage theory, an incremental damage evolution equation is formulated based on the multi-axial dynamic failure criterion of saturated concrete to more accurately represent the materail’s dynamic behavior under complex stress conditions. The proposed dynamic failure criterion demonstrates good agreement with test results and effectively predicts the dynamic strength of saturated concrete under multi-axial loads. Furthermore, the model was utilized for nonlinear analysis of reinforced concrete simple supported beams and compared with three plastic damage models. The results indicated that the model accurately predicts both hardening and softening behaviors, with a noticeable softening stage that highlights increased ductility and precise prediction of real-world performance in three-dimensional space.