Material modeling and numerical simulations of RC and SFRC slabs subjected to blast and impact loadings

Abstract

Material models for concrete and steel fiber reinforced concrete (SFRC) are introduced to simulate structural response of RC and SFRC slabs subjected to projectile impact or blast loading. First, a strain-rate-dependent orthotropic constitutive model that directly determines the stress state from the stress-strain relations defined from the biaxial strength envelope is considered. The proposed concrete model is incorporated in the two-dimensional finite element numerical formulation based on Mindlin plate theory. In order to cope with the development of large deformation concentrated within the plastic hinge region after yielding of reinforcement, the bond-slip effect is also taken into consideration by introducing modified bending stiffness, which is determined from the energy conservation law. To verify the validity of the numerical model, numerical results are compared with experimental data. In addition, an improved material model for SFRC structures subjected to impact and blast loads is proposed. Based on the previously introduced orthotropic model for plain concrete, a strain rate dependent material for SFRC under the dynamic multiaxial loads is developed to account for the effect derived from the addition of steel fibers in the concrete matrix. The constructed multiaxial strength envelope of SFRC is verified through correlation studies with experimental data, and improved failure strains in the uniaxial stress-strain relation are also introduced to minimize the mesh size dependency in the numerical results. Numerical analyses were performed for experiments of SFRC slabs under projectile impact and blast loadings, and the proposed model effectively simulates the structural responses of SFRC structures while minimizing the mesh size dependency in the numerical results.