Predictive equations for fundamental period of steel moment frames considering the effects of irregularity in the floor plan and height and soil-structure interaction

Robust estimation of fundamental elastic period of the buildings is essential for obtaining realistic seismic base shear. Seismic design codes provide a variety of equations to calculate the fundamental elastic period of vibration for steel moment frame buildings. The empirical equations are mainly based on the building height and does not take into account the effects of irregularity and soil-structure interaction. In this paper, an empirical predictive equation is developed to estimate the fundamental elastic period of steel moment frames. The predictive equation includes parameters that represent irregularity effects and soil-structure interaction . The database used in this study consists architectural and geotechnical data for 45 building cases. The proposed predictive equation shows satisfactory accuracy. The predicted results are then compared to the values obtained from Iranian 2800 seismic design code, ASCE7-16 and UBC-97. The proposed predictive equation is also verified by 10 fundamental elastic periods obtained from analytical models. The fundamental elastic period obtained using the predictive equations are specifically more accurate for mid- and high-rise buildings compared to seismic design codes. The values obtained from seismic codes are well below the realistic values for the buildings.