Active Control over Failure of RC Members by Application of Interrelation between Artificial Pre-Crack and Non-Orthogonal Crack

1)为了明确混凝土构件人工预裂缝与剪力引起的剪切裂缝的相互关系，进行了一系列的试验研究。在单调荷载和循环荷载作用下，人工预裂均能有效阻止新裂纹的扩展，从而提高混凝土构件的承载力和延性。当预裂缝与新裂缝夹角小于30°时，沿预裂缝形成新裂缝，构件承载力下降。2)采用增强主动裂纹法的非正交涂抹裂纹模型作为本构律处理具有交集的非正交裂纹。通过与试验结果的比较，验证了该模型能较好地预测相互作用裂纹的行为。3)基于实验事实和分析方法，对预埋塑料板模拟预裂缝混凝土构件的抗剪性能进行了研究。结果表明，所提出的节点单元对连续板的建模有较好的效果。4)通过多向荷载作用下的RC板结构试验，验证了本文提出的非正交裂缝模型的准确性。结果表明，以22.5°相交角为阈值的主动裂纹法能较好地预测非正交裂纹间的相互关系。此外，还验证了该模型在由高强混凝土和高强钢筋组成的结构中的应用。5)假设热应力为预裂缝的引入源，通过实验明确了高温下混凝土中预埋钢的抗拉刚度行为。将其表现特征纳入结构数值分析系统。

1) In order to clarify the interrelation between artificial pre-crack induced in concrete member and shear crack caused by shear force, a series of experiments was performed. Under both monotonic and cyclic loading, the artificial pre-creak prevented propagation of new share crack and then the capacity and ductility of RC member increased. On the contrary, when the angle between pre-crack and new crack because less than 30 degree, the capacity of member was decreased owing to the new crack formed along the pre-crack.2) Non-orthogonal smeared crack model of enhancing active crack method was adopted as a constitutive law to deal with non-orthogonal cracks with intersection. Comparinson with the experimental results verified that the proposed model could well predict the behavior of cracks with mutual interaction.3) Shear behavior of concrete members with embedded plastic plates, as devices to emulate pre-cracks, was studied based on both experimental facts and analytical approach. As a result, proposed joint element had a beneficial effect on modeling consecutive plates.4) The accuracy of the proposed non-orthogonal crack model was verified with experiments of RC plate structures under multi-directional loading. The result showed that active-crack method, which defined Intersection angle of 22.5 degrees as a threshold, could well predict interrelation between non-orthogonal cracks. In addition, the application of the model for structures that consist of high strength concrete and high strength reinforcing bars was proven.5) Because thermal stress was assumed as an introduction source of pre-cracks, the tension-stiffness behavior of embedded steel in concrete under high temperature was clarified experimentally. The manifested characteristics were incorporated into the structural numerical analysis system.