Ultra-High Performance Fiber Reinforced Concrete Structures - Macroscale Analysis with Mesoscale Lattice Discrete Particle Models

本研究开发了纤维增强水泥复合材料（FRCC）结构构件的宏观计算框架，特别关注超高性能混凝土（UHPC）。UHPC是一种FRCC，通过精细分级的水泥基体和高钢纤维体积，获得了优于钢筋混凝土的机械性能。分析UHPC结构部件的一个关键障碍是涉及复杂的断裂力学，然而，晶格模型模拟的最新进展为模拟离散裂纹提供了一个计算效率高的平台。晶格离散粒子模型（LDPM）可以通过中尺度本构关系来预测混凝土的行为，其中材料的破坏通过拉伸和压实中的断裂和内聚以及压缩下的孔隙崩塌来表示。LDPM已经成功地集成到一个小规模的商业有限元框架中，如果可以克服计算障碍，它将成为研究全尺寸UHPC结构的载荷变形响应的一个有吸引力和可访问的选择。该研究的主要目标是提供一个经过验证的计算建模协议，能够对全尺寸UHPC组件（如梁、柱、板）的倒塌进行结构分析，包括离散开裂、纤维基质相互作用和薄壁行为。政府和工业界最近的努力重点是在运输结构、高层建筑和防爆中广泛实施UHPC。这项工作需要时间来催化，很大程度上是因为用于分析UHPC结构部件加载崩溃的计算工具尚未开发出来。本研究旨在克服现有的计算障碍，为研究人员、政府和工业界提供一个有用的UHPC结构分析工具。这项研究的综合教育和推广目标将结合多尺度计算框架和动手实验，向学生介绍研究的回报和基本的工程原理。弗吉尼亚理工大学的工程多样性增强中心（CEED）正计划在中学的暑期课程中研究水泥基复合材料的张力、压缩和开裂。UHPC模块将为虚拟游戏环境“第二人生”中的弹性和可持续基础设施虚拟中心开发，以培养学生的研究兴趣。

This research develops a macroscale computational framework for fiber-reinforced cement composite (FRCC) structural members, with a specific focus on ultra-high performance concrete (UHPC). UHPC is an FRCC that attains superior mechanical properties to reinforced concrete through a finely graded cement matrix and a high steel fiber volume. A key hurdle to analyzing UHPC structural components is the complex fracture mechanics involved, however recent advances in lattice model simulation have provided a computationally efficient platform for simulating discrete cracking. Lattice discrete particle models (LDPM) can predict concrete behavior through mesoscale constitutive relationships where failure of the material is represented through fracture and cohesion in tension and compaction and pore collapse under compression. The LDPM has been successfully integrated into a commercial finite element framework at small scales, making it an attractive and accessible option for studying the load-deformation response of full-scale UHPC structures if computational hurdles can be overcome. The principal goal of the research is to deliver a validated computational modeling protocol capable of performing structural analysis to collapse of full scale UHPC components (e.g., beams, columns, plates) including discrete cracking, fiber-matrix interaction, and thin-walled behavior.Recent efforts by government and industry are focusing on broad implementation of UHPC in transportation structures, high-rise buildings, and blast protection. This effort is taking time to catalyze, in large part because computational tools for analyzing UHPC structural components loaded to collapse have yet to be developed. This research aims to overcome existing computational hurdles to deliver a useful structural analysis tool for UHPC to researchers, government, and industry. Integrated education and outreach goals for this research will pair the multiscale computational framework with hands-on experiments to introduce students to the rewards of research and to fundamental engineering principles. The Center for the Enhancement of Engineering Diversity (CEED) at Virginia Tech is planning middle school summer sessions to study tension, compression, and cracking in cement-based composites. A UHPC module will be developed for the Virtual Center for Resilient and Sustainable Infrastructures, hosted in the virtual gaming environment Second Life, to foster student interest in research.