Evaluation of seismic behavior and collapse capacity of dual RC frame-shear wall structures considering...

The influence of soil-foundation-structure interaction (SFSI) on seismic performance continues to be extensively investigated, yet limited attention has been given to reinforced concrete (RC) dual systems comprising shear walls and moment-resisting frames. This research explores the effects of SFSI on seismic demand distribution between these components across varying building heights and soil conditions. Three RC structures (5-, 10-, and 15-story) were designed per ASCE 7-22 and ACI 318 - 19 for soil types C and D accounting for both fixed-base and flexible-base scenarios, resulting in 12 cases. Inelastic time history, incremental dynamic analysis (IDA), and pushover analyses were conducted using OpenSees. Key response parameters, including capacity curves, inter-story drifts, plastic hinge rotations, and damage distribution, were evaluated, and collapse fragility curves were developed. Results indicate that SFSI increases plastic hinge rotations by up to 65% on soil type D and 36% on soil type C, with the greatest effects in shorter buildings. Although SFSI had minimal impact on taller structures at the design-level earthquake, IDA results reveal a substantial increase in collapse probability at high seismic intensities due to excessive displacements and amplified P-Delta effects. SFSI reduced collapse resistance margins by up to 35%, highlighting deficiencies in current design codes. These findings underscore the necessity of incorporating SFSI effects in seismic design to enhance the accuracy of seismic demand assessments and improve safety, particularly for RC dual systems on softer soils.