Investigating structural behavior and failure modes of thick concrete slabs under different contact shapes of dynamic impact load

Abstract In this study, reinforced concrete slabs were tested using a drop tower to develop a finite element (FE) model capable of accurately predicting structural behavior and damage under high loading rates, considering various parameters. The FE model was constructed using LS-DYNA software to simulate the impact of a low-velocity projectile on both plain and doubly reinforced concrete slabs, accounting for flat, hemispherical, and conical projectile nose shapes and varying drop heights. Two concrete material models, MAT_159 and MAT_145, were implemented and compared. Different approaches to apply the impact force, using both rigid and solid element-based projectiles defined with two material models (MAT_001 and MAT_020), were also explored to investigate the effect of shock wave reflections within the impacting body on the failure behavior of RC slabs. The selected material models were systematically validated against available test data and relevant literature. Through a parameter variation and a comparative study, the research identified and analyzed various phenomena, including spalling, scabbing, penetration, cracking, punching cone formation, displacement, and impact force characteristics. The comprehensive modeling approach was presented in detail and the robustness of LS-DYNA software to model and simulate RC under impact loading with heavy mass was put to the test, using the explicit time integration method.