Floor Spectra of MDOF Nonlinear Structures

In this article, the influence of nonlinear behavior of multiple degree of freedom (MDOF) primary structures on floor response spectra is investigated by means of simple structural models. The cases of shear beam type as well as of capacity-designed plane frames were studied. It is shown that, in general, but not always, nonlinearity of the primary structure has a beneficial effect on floor spectra. However, higher mode response may be amplified due to nonlinear behavior. The issue of a one story structure exhibiting torsionnal response has also been addressed and some important properties are highlighted.