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

本研究以超高性能混凝土(UHPC)为研究对象，建立了纤维增强水泥复合材料(FRCC)结构构件的宏观计算框架。超高性能混凝土是一种FRCC，它通过细级配水泥基质和高钢纤维掺量获得优于钢筋混凝土的力学性能。分析超高性能混凝土结构构件的一个关键障碍是复杂的断裂力学，然而格子模型模拟的最新进展为模拟离散开裂提供了一个计算高效的平台。晶格离散颗粒模型(LDPM)可以通过细观本构关系来预测混凝土的性能，其中材料的破坏表现为拉伸和压实时的断裂和内聚，以及压缩时的气孔坍塌。LDPM已经成功地集成到一个商业有限元框架中，如果能够克服计算障碍，它将成为研究全尺寸超高性能混凝土结构载荷-变形响应的一个有吸引力的和可行的选择。这项研究的主要目标是提供一种有效的计算建模协议，能够对全尺寸超高性能混凝土构件(如梁、柱、板)的倒塌进行结构分析，包括离散裂缝、纤维-基质相互作用和薄壁性能。最近，政府和行业的努力集中在交通结构、高层建筑和爆炸防护中广泛应用超高性能混凝土。这项工作需要时间来催化，这在很大程度上是因为用于分析加载到崩溃的超高性能混凝土结构组件的计算工具尚未开发出来。这项研究旨在克服现有的计算障碍，为研究人员、政府和行业提供一个有用的超高性能混凝土结构分析工具。这项研究的综合教育和推广目标将把多尺度计算框架与动手实验相结合，向学生介绍研究的回报和基本的工程原理。弗吉尼亚理工大学工程多样性增强中心(CEED)正在计划中学暑期课程，学习水泥基复合材料的拉伸、压缩和开裂。将为虚拟游戏环境Second Life托管的弹性和可持续基础设施虚拟中心开发UHPC模块，以培养学生对研究的兴趣。

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.