U.S.-Czech Engineering Research on Softening Damage, Fracture and Size Effect in Concrete Structures Under Dynamic and Cyclic Loads

这个由西北大学的Zdenek Bazant和捷克技术大学的三位研究人员Zdenek bittner、Milan Jirasek和Jan Vitek共同完成的美国-捷克研究项目，将重点研究建筑物和桥梁框架中的非弹性铰链，这些铰链在地震、爆炸或冲击等动态或循环载荷下会逐渐损坏并表现出软化。这种损伤可以分布在许多非弹性铰链上，也可以局限在其中的一些铰链上。巴赞特博士和他的捷克合作伙伴指出，局部化是一种危险的现象，因为它会导致坍塌更快地发生。该项目将对定位问题进行系统、理论和数值研究。还将研究混凝土在模拟钢筋作用下的侧向约束下的逐渐退化和断裂，并将局部化和断裂的分析扩展到梁的剪切破坏。将特别注意软化局部化和拉伸、剪切和压缩断裂所带来的尺寸效应。研究结果有望帮助预测混凝土结构对动力和循环荷载的抵抗力，从而有助于更安全的设计。该项目在力学和材料工程方面实现了促进科学知识的计划目标，使美国和东欧的专家能够在共同感兴趣和能力强的领域结合互补的人才和共享研究资源。?？

INT 9531299 Bazant This U.S.-Czech research project between Zdenek Bazant of Northwestern University and three researchers from Czech Technical University, Zdenek Bittnar, Milan Jirasek and Jan Vitek, will focus on inelastic hinges in frames of buildings and bridges that undergo progressive damage and exhibit softening resulting from dynamic or cyclic loading such as that caused by earthquake, blast or impact. Such damage can remain distributed over many inelastic hinges or it can localize in only some of them. Dr. Bazant and his Czech partners note that localization is a dangerous phenomenon because it can cause collapse to occur more rapidly. This project will involve a systematic, theoretical and numerical study of the localization problem. The progressive degradation and fracture of concrete in compression under lateral confinement simulating the effect of reinforcement will also be studied, with analysis of localization and fracture extended to the shear failure of beams. Particular attention will be devoted to the size effect brought about by localization of softening and by fractures in tension, shear and compression. Results are expected to help make predictions of concrete structures' resistance to dynamic and cyclic loading more realistic and subsequently contribute to safer designs. This project in mechanics and materials engineering fulfills the program objective of advancing scientific knowledge by enabling experts in the United States and Eastern Europe to combine complementary talents and share research resources in areas of strong mutual interest and competence. ??