Nonlinear analysis of commercial aircraft impact on a reactor building—Comparison between integral and decoupled crash simulation

Abstract

Since 9/11, the crash of a commercial aeroplane on the reactor building of a nuclear power plant is a realistic design scenario. Before that the structural behaviour under a crash of a military plane was investigated by a procedure using load-time functions (Riera, 1968). Thereby, the computation of the load-time-function was based on a conceptional model considering the main stiffness parts and masses by discrete elements. With respect to the homogeneous structural set-up of a military plane, the application of this model and the derived load-time-function applied as lumped load case seems very feasible. Contrary thereto the structural set-up of a commercial aeroplane, with e.g. the high mass concentration of the turbine or the high stiffness of the wing box compared to other parts, is different. This can be counteracted by using a more detailed finite element (FE) model for the computation of the load-time-function and by dividing the load case for the reactor building in different main load zones.Although this represents a more detailed investigation, the procedure of using a load-time-function still has the disadvantage to separate the real scenario into two steps. Thereby, the direct interaction between the structure and the aeroplane including all softening effects due to material respectively structural compliances is neglected. This leads to the general conclusion that by applying load-time-functions the results are conservative compared to the real behaviour.Due to the increased capabilities of numerical software solutions it is also possible nowadays to carry out integral crash simulations, combining all effects within one simulation. Compared to the procedure of using load-time-functions, the numerical complexity and therefore the amount of work for this integral method are increased.Within this paper both procedures (load-time function by detailed FE-model and the integral method) are exemplarily compared to each other by a crash analysis of an Airbus type A320 with different velocities (80, 120 and 160m/s) on simplified reactor building. The final evaluation is carried out by the maximum displacement of the reinforced concrete reactor building wall being a criterion for the integrity of the building. With respect to the results it could be shown, that the procedure using load-time-functions has limitations for the investigation of some scenarios. This could finally lead to the decision that for the design process of new nuclear power plants the application of the integral method comprehends advantages that justify the additional efforts.