About the strain-rate effect in HJC model

• HJC implements the strain-rate effect differently from other models (e.g. K&C). • Further study is necessary to know which implementation method is valid for concrete-like materials. • Several practices used in the original HJC model are questionable. • HJC model underestimates strain-rate effect in compressive domain. • A modified measurement of strain-rate effect in the HJC model is proposed. The strain-rate effect in HJC model is evaluated in this paper. Based on a comparison of strain-rate effects between the HJC and KC models, it shows that the determination and implementation procedures in the HJC model lead to smaller strain-rate effect. Some problems on the determination of strain-rate effect in the HJC model, i.e. the utilisations of the ‘leftward’ pressure correction, over-simplified strength curve and the cross-domain stress data, are discussed, which cause the underestimation of the strain-rate constant C . A more logical and practically-applicable ‘rightward’ pressure correction method is proposed to determine the strain-rate effect in the HJC model. The strain-rate effect determined from the high-pressure data is larger than that determined from the uniaxial compressive data, which facilitate further study on the pressure-dependent strain-rate effect.