A benchmark of numerical simulations of projectile impacts on reinforced concrete (RC) slabs has been launched in the frame of OECD/NEA/CSNI research program under the acronym IRIS. The goal of the research program is to simulate RC structural, flexural and punching, behavior under soft and hard missile impact. The first phase the IRIS_2010 was a blind prediction of the tests performed ant VTT facility in Espoo, Finland. The results showed significant scatter of the results for both flexural and punching simulation. The IRIS_2012 is the second, post-test, phase of the benchmark with the goal to improve simulations and reduce the scatter of the results. Based on the IRIS_2010 recommendations and to better calibrate concrete constitutive models, a series of tri-axial tests as well as Brazilian tests ware performed as a part of the IRIS_2012 benchmark. 25 teams from 11 countries took part in this exercise. Majority of participants were part of the IRIS_2010 benchmark. Participants showed significant improvement in reducing epistemic uncertainties in impact simulations. Several teams presented both FE and simplified analysis as per recommendations of the IRIS_2010. The improvements were at the level of simulation results but also at the level of understanding of impact phenomena and its modeling. However, due to the complexity of the physical phenomena and its simulation (high geometric and material nonlinear behavior) and inherent epistemic and aleatory uncertainties, the scatter remains important especially comparing to conventional, linear structural engineering analysis. The next goal is to further reduce the scatter and to concentrate on impact induced structural vibrations.
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