Upper bound frequency-dependent strains imposed on deep underground box-shaped structures under shear wave field of motion with different incident angles

This article investigates seismic demands of underground structures with a rectangular section in a twodimensional framework subjected to complete passage of shear wave field of motion. The wave field is considered to have different incident angles with the structure. Using the finite element approach, frequencydependent strain transfer functions for different parts of the structure are estimated. The transfer functions convert maximum free field shear strains to the uppermost strains imposed on structural sections. It is shown that maximum demands would not happen simultaneously for different parts of the structure. Also, critical frequencies of excitation and dominant incident angles may differ from each structural section to the other one. In the last part, simplified equations that cover dynamic characteristics of the problem and influences of different incident angles are suggested as correction factors to modify the strains commonly calculated from traditional static approaches.