Enhancement of engineering models for simulation of soft, and hard projectile impact on reinforced concrete structures

Protective Reinforced Concrete (RC) barrier walls of nuclear or industrial facilities are required to withstand accidental or intentional missile impact. The missiles (projectiles) can be classified as hard, semi-hard or soft. In particular, an airplane crash on a reinforced concrete structure causes local and global damage to the structure. Local damage mechanisms are usually associated with the impact of hard aircraft components such as engine shafts and wing boxes. In the event of a hard impact, the contact actions and target reactions are strongly coupled and therefore the calculation of capacity and damage effects is very sophisticated. There are various analysis methods for modelling both, hard and soft impacts. In this regard, empirical and semi-empirical models can be considered to calculate the load-bearing capacity in a simplified way with a few input parameters. However, validated numerical Finite Element (FE) simulation models allow further investigation on damage mechanism as well as detailed evaluation of stresses and strains in concrete and reinforcement. Hence, this paper investigates the efficiency of the existing analytical approaches as well as numerical simulation methods in predicting the load-bearing capacity of rc structures under hard and soft impact loads. Moreover, a novel simplified mechanical analytical method is proposed concerning hard impact loads. The mechanical principles are based on a nonlinear two degree of freedom (TDOF) system by Schluter (Schluter, 1987), which was extended for applications on hard impact scenarios considering the interaction between the impacting projectile and the rc target as well as penetration process of the projectile. FE-simulations and experimental test results of recent and ongoing research projects are presented and have been used for validation purposes and investigations.