The flexural and shear seismic demand for an isolated footing is based on the actual seismic analysis responses at the bottom of the column or the plastic hinging moment in the column at bottom. The frame analysis for the entire pier is carried out for applied dead and EQ loads and responses for Seismic Load Groups in LFD or Extreme Event Seismic limit state are determined. When the column design is done, program determines the plastic hinging moment in the column as well. Therefore, it is required that you first do the design of the column and then carry out the footing design for seismic loads. Program then determines the soil pressure / pile reaction based on the seismic axial force and biaxial moments at the base of the column. This is reported either as seismic soil pressure or seismic pile reaction. The critical is chosen after comparison of all load combinations. Based on this critical value, moment is computed at the face of support. It is checked if this is less than or equal to plastic hinging moment with an additional factor (by default 1.2). If the seismic demand is less footing is designed for it. However, if the plastic hinge moment is smaller, program designs for that value. The design for combined footing is somewhat similar to cap. For that a continuous beam model is solved for dead loads and plastic hinging moments applied at the column positions. The results are compared to the results obtained from the actual seismic response values at bottom of column. Smaller of the two sets at every check point along the length is then used as the controlling moment.