Evaluating Damage Indices for Adjacent 3D Steel Structures Considering SSSI Effects and Assessment of Seismic Performance in Time/Frequency Domain

Seismic waves of structural vibrations propagating through the soil and transmitting to other structures, and the effect this has on seismic performance, have recently come up due to the result of recent ground movements originating in soft soil zones like Mexico City. In regions with densely built structures, this vibration may have a significant impact on structural responses. The purpose of this research is to evaluate the seismic performance of a single structure on soil (Soil-Structure Interaction, or SSI) vs. that of a pair of similar structures with differing soil conditions (Structure-Soil-Structure Interaction, or SSSI). Recent research suggests that damage risks may increase due to the SSSI impacts. The studied structure is a three-dimensional, six-story steel building with a foundationally sound moment and braced frames lateral force resisting system. To account for the non-linear behavior shown by SSSI and SSI models, a three-dimensional steel structure is presented in OpenSEES. For simulating the soil easily under the foundations and between structures, the nonlinear Beam-on-Nonlinear-Winkler-Foundation (BNWF) model is employed. There is a meter of space between structures. Therefore impact between buildings is prohibited. The SSSI and SSI systems are examined using 11 horizontal components. Ground motion magnitudes ranges from Mw = 5.0 to Mw = 8.5, soil shear velocity varies from Vs30=185 m/s to Vs30=365 m/s, and distance from faults goes from 10 km to 50 km. The two orthogonal horizontal components of selected seismic ground motion stimulate the system. Inter-story drift ratio, roof displacement, and plastic hinge rotations of structural elements are among the reactions of importance. In the SSSI and SSI models, the Park-Ang damage index is utilized to calculate the local and global damage index. This damage indicator is divided into two categories: deformation and energy-based indices. The current study's findings show that the SSSI model increases the roof displacement response by up to 58%. When the SSI and SSSI cases are compared, it is discovered that the SSSI case increases the inter-story drift ratio by 118% in the moment frame and by 53% in the braced frame. In addition to this, it is shown that,  in general, a second structure may have a significant impact on the frequency amplitude of a system that is adjacent to it. According to the data, the amplitude of the power spectrum density in the SSSI model is more than 44.6% higher than that which is found in the SSI model. According to the findings, the damage index predicted by SSSI models is 32% greater than that predicted by SSI models. It is important to keep in mind that constructing a second building next to an existing one is often counterproductive and raises the possibility of damage occurring in both of the structures. As a result of the findings, it is clear that more study into SSSI phenomena and their influence on structural seismic risk is necessary. This is because it has been shown that adjacent buildings may significantly increase a structure's vulnerability to earthquakes.