Numerical predictions of concrete slabs under contact explosion by modified K&C material model

Abstract

To precisely predict the failure performances of cratering and spallation in concrete slabs under the contact explosion, three modifications were made to the original K&C (Karagozian & Case) material model that is #72REL3 in LS-DYNA, i.e. the tensile damage accumulation, relationship between the yield scale factor and damage function, as well as the tensile DIFt. The mechanical properties of normal weight concrete simulated by the modified model were validated by a series of single finite element numerical tests, including unconfined uniaxial compression, triaxial tension and dynamic tension tests. Two field tests were then conducted to study the failure modes of concrete slabs under contact explosion, as well as to verify the modifications. A new erosion criterion referring to the tensile damage was proposed to improve the simulation of the tensile failure of the concrete slab. The modified model and erosion criterion were implemented in LS-DYNA with the user-defined material procedure. The corresponding predictions by the original K&C model were also presented to demonstrate the improved effects of the modifications. Sensitivity analysis of the proposed erosion criterion and tensile DIFt was carried out to investigate the stability of the modified model.