This chapter firstly presents a new 3D mesoscale model,in which random distribution of coarse aggregate with random shapes and sizes in mortar matrix is simulated,to analyze the mechanical behavior of unreinforced concrete under static and dynamic load-ings.A good agreement is observed between the numerical results and test data.The effects of mesoscopic components such as aggregate size,mortar,and ITZ on the static and dynamic responses in uniaxial,biaxial and triaxial stress states are analyzed.The 3D mesoscale model is then extended to include random distribution of 3D steel fibres to simulate the static and dynamic responses of Steel Fiber Reinforced Concrete (SFRC) specimen.The static and dynamic responses in uniaxial,biaxial and triaxial stress states of SFRC,as well as the effects of fibre volume percentage on the responses are investigated.Numerical results agree well with test data.Finally,the proposed 3D mesoscale concrete model is extended and modified to predict the projectile penetration of concrete in-filled rock-rubble overlays.The effects of the diameter,compressive strength and the volume ratio of rock-rubbles,the strength of in-filled concrete as well as the incident velocity,oblique angle and hit position of the projectile on penetration depths of rock-rubble overlays are analyzed numerically.
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