Study on the size effect of dynamic tensile strength in lightweight concrete using Leca aggregates at the mesoscopic level

To investigate the influence of volume fraction of lightweight aggregate concrete on dynamic tensile strength and size effect, theoretical derivation and microscopic numerical simulation are combined in this study, and a dynamic hybrid fracture cohesive zone constitutive model for lightweight aggregate concrete to characterize the tensile behavior considering strain rate at microscopic scale. The research reveals that, for geometrically similar specimens of various sizes, the direct tensile strength with different aggregate volume fractions exhibits differing degrees of improvement with increasing strain rates. The tensile strength gradually decreases as volume fraction increases. The established coupling function incorporating strain rate, specimen size, and aggregate volume fraction accurately characterizes the dynamic tensile strength variation. In addition, a theoretical framework is proposed to provide a microscopic understanding of the static-dynamic size effect. This framework facilitates the estimation of the dynamic tensile strength under specific volume fraction, specimen size and strain rate conditions.