Study on Seismic Performance of Frame–Shear Wall Split-Foundation Structures with Shear Walls on Both Grounding Ends

This study focuses on the fundamental mechanical behavior of frame–shear wall split-foundation structures with shear walls at both upper and lower ground ends, investigating their basic mechanical characteristics, internal force redistribution patterns, and the influencing factor of intra-stiffness ratio on seismic performance. From the analysis results, it can be found that the relative drop height of frame–shear wall split-foundation structures significantly affects their internal force patterns. Shear-bending stiffness should be adopted in stiffness calculations to reflect the stiffness reduction effect of drop height on lower embedding shear walls. In frame–shear wall split-foundation structures, the existence of drop height causes upper embedding columns to experience more unfavorable stress conditions compared to lower embedding shear walls, potentially preventing lower embedding shear walls from serving as the primary seismic defense line. Strengthening lower embedding shear walls to reduce the intra-stiffness ratio can mitigate this issue. Performance evaluation under bidirectional rare earthquakes shows greater along-slope directional damage than cross-slope directional damage. Increasing shear wall length to reduce the intra-stiffness ratio improves component rotation-based performance, but shear strain-based evaluation of upper embedding shear walls indicates a limited improvement in shear capacity. Special attention should therefore be paid to along-slope directional shear capacity of upper embedding shear walls during structural design.