Mesoscopic finite element analysis on dynamic direct tensile failure of lightweight aggregate concrete and corresponding size effect

A comprehensive finite element analysis at the mesoscopic level has been conducted into the complex topic of size effect coupling dynamic strain-rates. Taking the lightweight aggregate concrete (LWAC) dumbbell-shaped samples as the object of numerical investigation, the influence of strain-rate (with the range of 10⁻⁵/s ∼ 100/s) on direct-tensile failure of LWAC (including different lightweight aggregate volume fractions [Formula: see text] = 40%, 30% and 20%) was discussed. Subsequently, the structure size of LWAC samples was further expanded (width W = 100, 200 and 300 mm) and the dynamic size effect on direct-tensile strength was investigated. Numerical results show that both the direct-tensile strength and its corresponding size effect of LWAC exhibit a strain-rate dependent behaviour. The increasing strain-rate can gradually weaken the size effect of LWAC and direct-tensile strength would be independent to the structure size as the strain-rate reaches the critical strain-rate. The increasing lightweight aggregate volume fraction can reduce direct-tensile strength. Furthermore, a dynamic size effect model establishing the direct link between the strain-rate effect and size effect was proposed, which can quantitatively predict the dynamic direct-tensile strength of LWAC.