Nonlinear Seismic Response of a Base-Isolated Liquid Container Having a Bottom-Mounted Submerged Internal Block

This paper examines the combined effects of an elastomeric rubber bearing and a submerged internal block on the nonlinear seismic performance of a rigid rectangular liquid container under earthquakes with various frequency contents. A nonlinear finite element model is developed incorporating a Coupled Eulerian and Lagrangian (CEL) formulation to address the nonlinear sloshing effects of liquid. The developed model has been validated using the benchmark results available in the literature. Parametric analyses have been carried out for different internal block configurations and isolation parameters to study their influence on essential seismic responses, namely slosh amplitude, hydrodynamic pressure components, and base shear. Results show that isolation is effective in shifting the fundamental sloshing frequency along with significant reductions in hydrodynamic pressure and total base shear. On the other hand, an internal block further improves the slosh suppression effectiveness. The nonlinear analyses also yield higher sloshing amplitudes compared to their linear counterparts, demonstrating the necessity of nonlinear modeling for accurate freeboard estimation. Overall, the present study establishes that the hybrid implementation of a submerged block and rubber bearing isolation is an effective vibration control strategy for liquid storage tanks subjected to earthquakes with varying frequency characteristics.