Study on dimensional effect of lightweight aggregate concrete based on rate-dependent cohesive mesoscopic model

The research on the dimensional effect of concrete under quasi-static loading has achieved rich results. However, under impact loading, that is, at medium and high strain rates, due to the limitation of test equipment and the limitation of specimen size in laboratory tests, the dimensional effect of lightweight aggregate concrete (LWAC) at medium and high strain rates still needs to be studied in depth. In order to study the influence of size and strain rate on the compressive strength of LWAC under uniaxial dynamic compression, the constitutive relationship of mixed fracture cohesive considering rate effect is established, and then the uniaxial dynamic compression model of LWAC at meso-scale is generated. The results demonstrate that when the strain rate ε ̇ > 1 s − 1 , and the geometric size is constant, the compressive strength increases gradually with the increase of strain rate. When the strain rate is kept constant, the dynamic compressive strength increases with the increase of specimen size. When the strain rate ε ̇ = 200 s − 1 , and the specimen size increases from 100 mm to 300 mm, the compressive strength increases by 0.78 times. In addition, the proposed theoretical formula of dynamic dimensional effect is helpful to accurately predict the dynamic compressive mechanical properties of LWAC, and also provides a theoretical basis for the engineering structure design of large-scale LWAC under impact loading.