Coupled Experimental and Computational Investigation of the Interplay between Discrete and Continuous Reinforcement in Ultrahigh Performance Concrete Beams. II: Mesoscale Modeling

The first experimental campaign presented in the preceding Part I of this study is used to calibrate and validate a comprehensive computational framework called the lattice discrete particle model for fiber-reinforced concrete (LDPM-F). The model is then used to design the second experimental campaign that was also presented in the preceding Part I so that all beams fail in shear. Finally, the model is used to investigate and explain the observed failure modes, validate the fiber/reinforcement interplay effects postulated in Part I, and to analyze comprehensively the load-transfer mechanisms in the reinforced ultra-high performance concrete (R-UHPC) beams in both shear and flexural failure. This two-part study proves the effectiveness of coupling experimental analysis with comprehensive computational modeling to understand the behavior of structural members made from complex materials. Using this coupled understanding, detailed explanations of load-transfer mechanisms in shallow and deep beam shear failure as well as flexural failure are discussed and compared to simplified sectional analysis models showing the places of needed improvement in such models. These detailed discussions show the ability of the presented coupled approach to accurately predict these failure mechanisms and their dependence on fiber/reinforcement contents and their interplay. The presented accurate probing of different load-transfer mechanisms within the structural elements and how they vary during failure progression paves the road towards developing rigorous design formulations based on fundamental understanding of the complex mechanical behavior of these structural members. (C) 2021 American Society of Civil Engineers.