Universal Mathematical Model for Predicting the Ductility of Reinforced Concrete

本研究旨在建立一套能准确预测钢筋混凝土构件在反复荷载作用下的变形和延性的通用计算方法。重点研究了循环载荷下的断裂过程以及持续载荷下的变形和塑性过程.循环载荷下的断裂过程研究了循环载荷对沿着裂纹应力传递的影响。研究表明，在初始循环荷载作用下，沿裂缝沿着方向的剪切刚度大大降低.持续加载下的变形过程研究了持续加载对裂纹法向抗拉刚度的影响。明确了钢筋屈服后抗拉刚度的时变特性.分析系统的修正使用循环和持续条件下建立的本构方程。将加载通用本构方程引入分析体系。建立了钢筋混凝土的时变和路径相关本构模型，并对钢筋混凝土进行了动力分析.研究了反复荷载和持续荷载对钢筋与混凝土粘结性能的影响。提出了适用性强、精度高的修正节理单元。

The objective of this study is to establish the general computing method for accurately predicting the deformation and ductility of reinforced concrete members reversed cyclic loading. The Special attention was paid on the progress of fracture under cyclic loading and the progress of deformation and plasticity under sustained loading.1. Progress of fracture under cyclic loadingThe effect of cyclic loading on the stress transfer along cracks was investigated. It was clarified that shear stiffness along cracks is greatly reduced under initial reversed cyclic loading.2. Progress of deformation under sustained loading.The effect of sustained loading on the tension stiffness in the normal direction to cracks was investigated. Time-dependent behavior of tension stiffness was clarified after yielding of reinforcing bars.3. Modification of analytical systemUsing the constitutive equations developed under cyclic-and sustained. loading general constitutive equation was introduced to the analytical system. Time-dependent and path-dependent constitutive model was developed and dynamic analysis for reinforced concrete was succesively carried out.4. Development of Joint elementThe effect of cyclic and sustained loading on the bond behavior steel bar and concrete was investigated. Modified joint element was proposed with high applicability and high accuracy.