Strength and deformation characteristics of concrete under dynamic biaxial loading

Compressive tests on cubic specimens were conducted at different strain rates using a servo-hydraulic multiaxial testing machine. Considerable emphasis was laid on the dynamic strength and deformation properties of concrete in biaxial stress state. The lateral pressure was kept in proportion to the main axial load with the ratio of 0:1, 0.25:1, 0.5:1, 0.75:1 and 1:1 respectively at the strain rate ranging from 10(-5)/s to 10(-2)/s. From the test results it is revealed that the dynamic strength is enhanced with the increasing of strain rate. The shear failure envelope is enlarged by 2 % - 10 % in case of the strain rate increasing by one order of the magnitude compared with that under static loading. The modulus of elasticity also increases with the increasing of strain rate. The linear part of the stress-strain curves tends to extend as far as strain rate increases, while the curvature of the nonlinear part tends to diminish. Moreover, strain rate has little influence on the fracture modes of specimens in biaxial stress states.