RIA: Brittleness Effects on the Structural Response of Strain-Softening Materials

RIA：脆性对应变软化材料结构响应的影响

• 批准号: 9109416
• 负责人: Joseph Labuz
• 金额: $ 6.98万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-07-15 至 1994-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9109416&HistoricalAwards=false
• 关键词: RIA; Brittleness; Effects; Structural; Response

Strain softening is a characteristic displayed in several materials encountered in civil engineering. For example, rock, concrete, and dense soil exhibit the behavior where the tangent modulus decreases from an initial positive value and becomes negative as strain increases. When softening is involved with a structural component, however, an internal snap-back instability may occur, with the softening branch taking on a positive slope. Failures of this type would be catastrophic even in a displacement-controlled setting and must be prevented. The objective of this research is to develop and apply a theory of brittleness in order to predict the global behavior of a structure composed of a strain-softening material. An elastic-plastic constitutive law will be adoptive for the local strain components, while the softening behavior will be described in terms of displacement components through a cohesive-zone model of fracture. Experiments will be conducted in a closed-loop, servo-hydraulic testing system to capture the post-failure regime and to evaluate the necessary material parameters. The softening response of concrete beams in three-point bending will be studied by varying the geometry, size, and constraint, while recording the acoustic emissions from the failure process. Acoustic emission testing in proposed as a viable nondestructive technique to detect the onset of an instability. This research will provide an analytical explanation and present experimental evidence of the snap-through versus snap-back behavior of strain-softening beams.

应变软化是土木工程中遇到的几种材料所表现出的特性。例如，岩石、混凝土和致密土的切模量会随着应变的增加而从初始的正值减小到负值。然而，当软化涉及到结构部件时，可能会发生内部回跳失稳，软化分支呈正斜率。这种类型的故障即使在位移控制的情况下也是灾难性的，必须加以预防。本研究的目的是发展和应用脆性理论，以预测由应变软化材料组成的结构的整体行为。局部应变分量将采用弹塑性本构法，而软化行为将通过断裂黏结区模型用位移分量来描述。实验将在一个闭环伺服液压测试系统中进行，以捕捉失效后的状态并评估必要的材料参数。混凝土梁在三点弯曲中的软化响应将通过改变几何形状、尺寸和约束来研究，同时记录破坏过程中的声发射。声发射检测被认为是一种可行的无损检测方法。本研究将为应变软化梁的断通与断回行为提供分析解释和实验证据。