Seismic response of steel moment frame considering gravity system and column base flexibility

High ductility and architectural versatility characteristics make Steel Moment Frames (SMF) one of the most commonly used lateral resisting systems for building structures. Collapse assessment of such buildings are typically suffering from two modeling simplifications: 1) neglecting the gravity system model, and 2) neglecting column base flexibility by using idealized boundary conditions (i.e. fix or pin). This study assesses the seismic performance of an 8-Story SMF and takes into consideration the effects of the column-base flexibility and the inclusion of the gravity system in such assessment. The flexibility of the column-base connection is included by aggregating deformations of various components of the base connection while the gravity system is included by taken into consideration the continuous stiffness provided by the gravity columns. Nonlinear dynamic response history analysis using design level ground motions was used to compare the influence of the different properties on the story drifts and residual displacements. Moreover, using the FEMA P-695 methodology, the influence of these modeling simplifications on the collapse performance is established. Previous research indicates that the flexibility of column bases has a detrimental effect on the building's seismic performance. However, the positive effects that considering the gravity system brings evens out in the seismic behavior of the structure.