Dynamic Response of a Structure Exposed to Earthquake Rotational Components and Soil-Structure Interaction Effects

The effects of rotational (torsional and rocking) components of an earthquake are often neglected in dynamic analyses, as most modern codes only provide horizontal and vertical elastic spectral curves. However, neglecting these components can lead to the unrealistic results, especially when considering soil-structure interaction effects. Incorporating soil-structure interaction (SSI) significantly changes the behavior of structures, affecting their modes, shapes, and mass participation ratios. This emphasizes the importance of rotational modes and their impact on structural responses, including lateral and rotational displacement, velocity, and acceleration. The study aims to examine the effects of SSI while considering rotational earthquake motions on structural responses. Therefore, the Benchmark structure was placed on different soil types (very soft, soft, medium, and dense soil), and time history analyses were conducted. The results showed that rotational components significantly affect dynamic characteristics and structural performance indexes such as the fundamental period, base shear, inter-story drift ratios, maximum floor acceleration, and input energy. Taking rotational components into account is necessary for more accurate results, especially when the foundation is on soil with a shear velocity of less than 100 m/s.