Design of Soft Stories—A Simplified Energy Approach

Most specialists dealing with earthquake engineering agree that soft stories represent a major reason for buildings collapses during major earthquakes, but seismic forces acting upon soft stories have not yet been quantified. The author proposes an energy approach yielding equivalent static forces to be taken into account in the design of resisting elements of soft stories. It is based on interpolation between two extreme situations: uniform structures and rigid structures supported by a soft story. Although the solution is based on quantifying the plastic energy absorbed during the seismic motion, it is shown that the effective computations can be performed in the elastic range.