BRIGE: Damage Evaluation and Life-Cycle Assessment of Reinforced HPFRC Beam-Column Joints under Multi-Axial Loading

技术描述尽管结构材料取得了重大进展，但在地震期间，钢筋混凝土（RC）建筑物的灾难性梁柱接缝失效仍然是一个问题。在简单（平面）加载条件下，钢筋混凝土节点的行为和破坏机制已经得到了广泛的研究。目前的实践告诉我们，增加节点的尺寸或钢筋的数量，以提高节点的能力，防止过早破坏。然而，这种方法绝对是不可持续的。此外，正如在最近的地震中观察到的那样，这种做法并不总能防止节理区域的灾难性破坏，从而得出结论，节理在复杂（多轴）荷载条件下的行为仍然没有得到很好的理解。在本项目中，高性能纤维增强混凝土（HPFRC）将有选择地用于梁柱节点，以提高建筑物的结构性能，同时将额外成本降至最低。采用试验和计算相结合的方法，对钢筋混凝土和HPFRC节点结构进行损伤对比评估和全寿命周期成本评估。由于节理的载荷传递和材料在多轴载荷作用下的性能复杂，对节理进行分析是一项困难的任务。因此，将使用两个多轴（6自由度）加载单元对节理施加真实的加载和边界条件，并使用用于非接触变形测量（DIC）的数字图像相关系统获得全场三维应变图，以研究导致损伤起始及其进展直至完全破坏的临界变形状态。这些研究活动预计将产生对RC和R-HPFRC节点行为的重要新知识和理解，以及研究RC/增强hpfrc材料和节点行为的可靠计算工具。更广泛的意义和重要性提出的新方法有望在长期内改变RC梁柱节点的设计和施工。这个项目对社会的直接好处是提高了公共安全，以应对地震。另一个好处是增加了可持续性，减少了直接和间接的经济损失和环境影响。这个项目取得的成就将是朝着建设具有复原力和可持续性的民用基础设施的最终目标迈出的一大步。提出的接缝概念也广泛适用于其他类型的混凝土建筑，包括海上和核结构。从这些新的测试和测量方法中收集的数据将作为数值模拟和工程模拟新理论发展的基准，这在以前由于缺乏支持实验数据而无法考虑。扩大参与活动休斯顿大学（UH）是一所为西班牙裔服务的机构。休斯敦大学拥有近4万名学生，是美国最多元化的学生之一。将在三门课程中开发和引入教育模块，每年影响100多名学生的教育。由于校园固有的多样性，这些教育活动自然会接触到不同的受众。研究生和本科生将从代表性不足的群体中招募。与当地一所90%以上学生人数不足的高中合作，每年将组织一次实地考察，让25名学生参观UH校园并参加实践培训。此外，每年夏天将招募一名高中教师参与研究活动，并帮助开发高中物理课程的课程模块。通过开发的教育活动，高中教师、高中生、本科生和研究生将有机会相互交流，相互学习。课程模块将直接来源于研究成果，并在高中和大学阶段的课程中实施，从而自然地将研究与教育结合起来。这项研究是由工程教育和中心部的工程项目扩大参与计划的一部分，即工程项目扩大参与研究启动基金资助的。

Technical DescriptionDespite significant advances in structural materials, catastrophic beam-column joint failures in reinforced concrete (RC) buildings persist in being a problem during earthquakes. The behavior and failure mechanisms in RC joints have been extensively studied in the past and are well understood under simple (planar) loading conditions. Current practice tells us to increase the joint dimensions or the amount of reinforcing steel to enhance the capacity of the joints and prevent premature failure. However, this approach is definitely not sustainable. Additionally, as observed in recent earthquakes, this practice does not always prevent catastrophic failures in the joint region, leading to the conclusion that the behavior of joints under complex (multi-axial) loading conditions is still not well understood.In this project, high-performance fiber reinforced concrete (HPFRC) will be selectively used at the beam-column joints to improve the structural performance of buildings while keeping the additional costs at a minimum. Using experimental and computational methods, a comparative damage evaluation and life-cycle cost assessment of building with RC and HPFRC joints will be conducted. Analysis of joints is a difficult task because of the complex load transfer and the behavior of materials under multi-axial loading. Therefore, two multi-axial (6 degree-of-freedom) loading units will be used to impose realistic loading and boundary conditions on the joints, and a digital-image correlation system for non-contact deformation measurements (DIC) will be used to obtain full-field 3-D strain maps to study critical deformation states that lead to the initiation of damage as well as its progression until complete failure. These research activities are anticipated to yield critical new knowledge and understanding of the behavior of RC and R-HPFRC joints, and reliable computational tools to study the RC/reinforced-HPFRC material and joint behavior.Broader Significance and ImportanceThe proposed novel approach is expected to transform the design and construction of RC beam-column joints over the long-term. A direct benefit of this project to society is the improvement in public safety in response to earthquakes. An additional benefit is increased sustainability in the form of reduced direct and indirect economic losses and environmental impacts. The achievements in this project will be a large step in reaching the ultimate goal of resilient and sustainable civil infrastructures. The proposed joint concept also has broad applicability in other types of concrete construction, including offshore and nuclear structures. The data collected from these novel testing and measurement approaches will serve as benchmarks for the development of new theories for numerical modeling and engineering simulations, which could not be considered previously because of the lack of supporting experimental data.Broadening Participation ActivitiesThe University of Houston (UH) is a Hispanic-Serving Institution. The UH student body of nearly 40,000 students is one of the most diverse in the United States. Educational modules will be developed and introduced in three courses to influence the education of more than 100 students per year. Because of the inherent campus diversity, these educational initiatives will naturally reach a diverse audience. Graduate and undergraduate students will be recruited from underrepresented groups. In collaboration with a local high school with more than 90% underrepresented students, a field trip will be organized every year for 25 students to visit the UH campus and participate in hands-on training. In addition, one high school teacher will be recruited every summer to gain exposure to research activities and help develop a course module for high school physics courses. Through the developed education activities, high school teachers, high school students, and undergraduate and graduate students will have an opportunity to interact and learn from each other. The course modules will directly derive from the research findings and be implemented in high school and college level courses, thereby naturally integrating research and education.This research has been funded through the Broadening Participation Research Initiation Grants in Engineering solicitation, which is part of the Broadening Participation in Engineering Program of the Engineering Education and Centers Division.