Probabilistic Characterization of Bond Behavior at Rebar-Concrete Interface in Corroded RC Structures

在最近的一份报告中，国土安全部指出，老化的基础设施对国家经济健康构成的危险被认为与最近的金融危机构成的危险一样大。虽然老化本身不是结构失效机制，但它降低了基础设施对自然或人为灾害的稳健性和恢复能力。本研究将集中在腐蚀对老化钢筋混凝土（RC）结构的钢筋-混凝土界面粘结行为的影响这一被忽视的方面。本研究的结果将为建筑环境抗灾能力的新设计标准提供信息，其中允许/考虑在使用寿命期间与年龄相关的退化，并增强可用的状态评估工具，以全面评估老化RC基础设施的性能，进而可用于开发定量决策支持系统，以优化资源配置。该研究的跨学科性质（包括实验和数值研究）为研究生和本科生提供了理想的学习环境，并将为学生提供急需的风险管理统计和可靠性分析工具。PI致力于通过现有的校园项目在她的机构招募和留住代表性不足的本科生/研究生。研究的目的有两个：一是更好地了解腐蚀恶化对粘结行为的影响，二是将新获得的知识应用到结构和风险分析中。据此，规划了5项工作：(1)综合开展考虑腐蚀的单调加载和循环加载下粘结性能试验试验；(2)基于包含不确定性的试验数据评估键合模型参数；(3)通过贝叶斯更新方法概率地推导出考虑腐蚀效应的粘结应力-滑移本构规律；(4)将粘结恶化纳入结构分析，包括改进和扩大当前的设计标准，使用OpenSees实现和数值验证开发的本构关系；(5)通过案例研究，探讨腐蚀对风险量化的影响。该研究将提高对老化对结构性能影响的基本认识。键本构模型公式考虑了普遍存在的不确定性，并提供了一种严格的更新手段，无论何时有额外的实验数据可用，使不断更新的本构模型更加稳健。最重要的是，实施活动将为弹性设计的发展奠定基础，并使研究结构在极端灾害下的性能并适当考虑老化效应成为可能。

In a recent report, the Department of Homeland Security stated that the dangers posed by the aging infrastructure to the nation economic health are considered to be as great as those posed by the recent financial crisis. Although aging itself is not a structural failure mechanism, it decreases infrastructure robustness and resilience against natural or man-made hazards. This research will focus on the ignored/disregarded aspect of the corrosion effect on the bond behavior at the rebar-concrete interface of aging reinforced concrete (RC) structures. The results of this research will inform new design standards for disaster resilience of the built environment, where age-related deterioration is allowed/considered during the service life, and also enhance the available condition assessment tools to holistically evaluate the performance of aging RC infrastructure, which, in turn, can be used to develop a quantitative decision support system for optimizing resource allocation. The interdisciplinary nature of the research (including experimental and numerical studies) provides an ideal learning environment for graduate and undergraduate students, and will equip the students with much-needed statistical and reliability analysis tools for risk management. The PI is committed to recruiting and retaining underrepresented undergraduate/graduate students at her institution through existing campus programs.There are two research objectives: to better understand the corrosion deterioration on bond behavior, and to implement the newly obtained knowledge into structural and risk analysis. Accordingly, five tasks are planned: (1) conduct comprehensive experimental tests on bond performance under monotonic and cyclic loading considering corrosion; (2) assess bond model parameters based on the test data incorporating uncertainties; (3) probabilistically develop the bond stress-slip constitutive law with corrosion effect through a Bayesian updating approach; (4) incorporate the bond deterioration in the structural analysis, including enhancing and augmenting the current design standards, implementing and numerically validating the developed constitutive relation using OpenSees; and (5) conduct a case study to investigate the corrosion effect on the risk quantification. The research will improve the fundamental understanding of the age related deterioration effect on structural behavior. The bond constitutive model formulation considers prevailing uncertainties and provides a rigorous means for update whenever additional experimental data is made available, making the continuously updated constitutive model more robust. Most importantly, the implementation activities will lay the groundwork for the resilience design development, and make it possible to investigate the structural performance subjected to extreme hazards with appropriate consideration of the aging effect.