FE Analysis of Reinforced Concrete Structures Under Missile Impact Using Sub-modelling Technique
Abstract of the technical paper presented at:
SMiRT 25 Conference
Charlotte, North Carolina, USA
August 4-9, 2019
Genadijs Sagals, Nebojsa Orbovic and Christopher Cole
Canadian Nuclear Safety Commission
This paper describes the work conducted by the Canadian Nuclear Safety Commission (CNSC) related to the numerical simulations of reinforced concrete (RC) structures under deformable missile impact. The current paper is a continuation of the work conducted in the frame of the OECD/NEA IRIS (Improving Robustness Assessment Methodologies for Structures Impacted by Missiles) Phase 3 benchmark project.
The concrete mock-up with two simple structures attached, one welded and another bolted, was built and tested at the VTT Technical Research Centre in Espoo, Finland. This mock-up was impacted by three subsequent missiles with varying velocities in order to obtain the damage accumulation. To examine vibration transmission through the mock-up, the simple structures modelling equipment were attached to the rear wall of the structure, while the missile impact was at the centre of the front wall. The parameters of the missiles and the RC structure were selected to ensure a flexible behaviour of the RC target in the impact area with only moderate damages, specifically cracking and permanent deformation without perforation.
Detailed modelling of a large RC structure with all equipment attached leads to a very large finite element (FE) model. Therefore, the main objective of this work was to create a two-level FE model using a commonly used sub-modelling approach: first, analyze the vibrations of a reinforced concrete structure with simplified equipment modelling, and second, analyze in detail the equipment connected to it. This approach assumes uncoupled dynamic behaviour of the structure and the equipment.
The non-linear dynamic behaviour of the reinforced concrete slabs under missile impact was analyzed using the commercial FE code LS-DYNA. Both 3-D solid and 2-D shell FE models were employed for the target discretization. As the ultimate objective of this work is to model the entire structure over long time periods, a simplified combined shell-solid model with distributed (smeared) reinforcement was selected and validated. This model employs solid FE around an impact area and shell FE for the rest of the mock-up.
“Blind” (without knowing test results) FE predictions were compared to tests conducted at the VTT test facility. As a result, the FE model was revised to better match the test data. The revised model shows good agreement with the test results for both global (RC mock-up) and local (equipment) behaviour. To select adequate cut boundaries for sub-models, sensitivity analysis was conducted. The result of this analysis shows that cut boundaries should go only through un-cracked areas of concrete.
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