Impact of Ground Motion Incident Angle on Seismic Performance of Reinforced Concrete Frame Building Without and with Metallic Damper

In the current codes of designing, the seismic response of structures is evaluated based on the simultaneous effect of two orthogonal components of ground motion. Metallic dampers, known for their stable and efficient energy dissipation, are widely adopted in seismic design. This study investigates the influence of earthquake incident angle on the seismic performance of conventional and energy-dissipating structures using a five-story reinforced concrete (RC) frame building equipped with metallic dampers. To assess structural responses under design-basis earthquakes, nonlinear time-history analyses are conducted using 22 pairs of far-field ground motions. The effects of incident angle are examined by rotating orthogonal ground motion components from 0° to 180° in 10° increments, resulting in 19 angle cases. Key seismic demands—including maximum displacement, inter-story drift ratio, base shear, and damper energy dissipation—are evaluated. Results reveal that the incident angle significantly affects structural responses, and the critical angle producing peak demands varies with the response parameter. The addition of metallic dampers substantially enhances seismic performance by reducing response levels and increasing energy dissipation. These findings provide valuable insights for improving seismic design strategies for RC buildings with and without metallic dampers.