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.
