Biaxial Behaviour of Plain Concrete Subjected to Dynamic Compression with Constant Lateral Stress

This study investigates the dynamic biaxial behaviour of concrete by testing more than 60 cubic specimens on a custom-designed, servo-hydraulic- controlled machine. Each specimen was axially loaded in compression at a constant strain rate of 10 ^-5 , 10 ^-4 , 10 ^-3 or 10 ^-2 s ^-1 while two opposite side faces were subjected to a constant confining pressure and the other two side faces were free. The confining pressure applied to each specimen was 0, 30.5, 61.0 or 91.5 % of its uniaxial compressive strength. Test results indicate that the biaxial strength of concrete increases with strain rate at a reduced slope as confining pressure increases. The failure mode of the concrete specimens was basically unaffected by the strain rate. An empirical relation for the ultimate strength of concrete in a biaxial stress state was developed taking into account the effects of both confinement and strain rate.