Abstract Summary
The earthquake response of bridge cranes is a very important safety issue for industrial facilities, for example, nuclear plants. During an earthquake, the bridge crane is subjected to multi-impacts and frictional contacts between trolley wheels and girders, as well as between crane wheels and runways. In order to take into account such non-linear effects in the numerical simulation of bridge cranes under earthquake, firstly, an efficient explicit time integrator for the impact and frictional contact, based on the Central Difference (CD) scheme, is presented, where the constraints are treated with Lagrange multipliers. For the purpose of reducing CPU time, the explicit time integrator is only applied in the 3D contact areas with a fine time scale satisfying the stability condition, while an implicit time integrator is adopted in the other parts with a large time step. Thanks to the proposed hybrid approach, Rayleigh viscous matrix can be adopted only in the implicit partition, without reducing the critical time step in the explicit CD partition. Finally, three-dimensional explicit/implicit multi-time step simulations of bridge cranes under earthquake are carried out using the proposed explicit/implicit heterogeneous asynchronous time integrator (HATI) for non-smooth transient dynamics to predict the non-linear earthquake response of the experimentally tested bridge crane. The comparison between experimental and numerical results gives an overall satisfactory agreement in terms of displacements, accelerations and efforts transmitted to the anchorages.
