Influence of aggregate and interface properties on the impact response and scaling effect of RC beams: A mesoscale study

As a multiphase composite material, concrete exhibits complex mechanical responses under dynamic loads due to the heterogeneity of its internal mesoscopic components. Prototype tests are the most reliable methodologies to explore structural performance under dynamic loads, but they are limited by equipment, technology, and cost. Therefore, researchers typically adopt scaled tests to analyze the structural impact response. However, the dynamic response of the structure may not satisfy the classical similarity law and the reasons are under investigation. In this study, the relationship between concrete heterogeneity and scaling effect was explored preliminarily. Based on the drop hammer impact simulations, the mesoscale numerical models of four reinforced concrete (RC) beams (scale factors λ = 1/4, 1/2, 3/4, and 1) were established after considering the heterogeneity of concrete. The effects of aggregate content, aggregate elastic modulus, and interfacial transition zone (ITZ) strength on the impact response and their scaling effects were investigated. Finally, the Gaussian function was applied to describe concrete heterogeneity and analyze its relationship with the scaling effect. The results indicate that aggregate elastic modulus and ITZ strength have a minor effect on the impact response. However, increased aggregate content enhances the midspan displacement and displacement scaling effect in geometrically similar RC beams. The more substantial the concrete heterogeneity in the spatial distribution, the stronger the peak displacement scaling effect on geometrically similar RC beams.