Size Effect and Dynamic Fracture Parameters of Concrete Subjected to High Loading Rates

Concrete is the most used material in tall buildings, bridges, tunnels, and dams. Its uses vary from structural applications to pipes, pavements, and hardened shelters. Significant progress has been made in the static size effect of concrete, while the size effect on concrete strength has not received too much attention at high loading rates. No comprehensive experimental efforts have been conducted in the dynamic size effect on concrete strength, including aggregate and specimen size. This study presents a comprehensive experimental investigation of the dynamic size effect and fracture characteristics of concrete. The research involves about two hundred concrete specimens with various maximum aggregate sizes under tensile loading ranging over five orders of magnitude. The influence of structural size and aggregate size on the dynamic strength of concrete is explored using the Work of Fracture Method (WFM) and Size Effect Method (SEM). The experimental results indicate a considerable size effect in concrete subjected to dynamic loading, although the size effect on concrete nominal strength is weakened by increasing the loading rate and aggregate size. Besides, this treatment will help to create and calibrate new theoretical and numerical models. In this study, a rate and aggregate size-dependent model cable for predicting the concrete strength is proposed. This model can predict the nominal strength of concrete considering the coupled effects, including loading rate, specimen size, and aggregate size. The model is validated for concrete under loading rates over five orders of magnitude (10-4 to 10 1/s). The 2019 ACI code recently considered the size effect in the punching and shear design of beams based on significant progress in the static size effect, while its introduction for dynamic loading in design and codes needs further studies.