A new proposal for building resonance period range estimation during earthquakes considering soil-structure interaction

The study aims to estimate the mean period range of ground motions associated with building resonance, considering soil-structure interaction (SSI). The research employs a simple linear single-degree-of-freedom (SDF) model for the superstructure, with the foundation modeled as a circular geometry supported by equivalent Winkler springs to represent the soil. To validate the results, the dynamic characteristics of a fifteen-story steel office-government building in Los Angeles were applied to the model. The roof-level seismic response during the Northridge earthquake was compared to recorded sensor data. Initially, a comprehensive parametric study was conducted on the seismic response amplification of buildings, considering SSI effects. For this purpose, the seismic response and resonance periods were evaluated for nine building types (four, eight, and twelve stories with varying damping levels) using 109 seismic ground motion records resulting from 4905 time-history analyses. The findings indicate that high damping effects and SSI can increase the resonant period by up to 2 times. In the second phase, a new simplified formula based on non-dimensional frequency and damping ratio is proposed to estimate the mean period range of ground motions related to resonance. The equations for the lower and upper limits of the resonance frequency ratio range exhibit R-factors of 93 % and 99 %, respectively. Additionally, the effectiveness of the proposed formula is confirmed through comparisons with the results of a comprehensive database, including 43 full-scale soil-structure models subjected to seismic ground motions and forced vibration tests. All data points between the two surfaces represent the lower and upper limits, demonstrating the good accuracy of the proposed formula.