Equivalent linear ductility design of soil-structure interaction systems

The purpose of this paper is to propose a new semi-explicit ductility design method for a shear building model taking into account dynamic soil-structure interaction. The shear building model is supported by swaying and rocking springs and by the corresponding dashpots. Design earthquakes are defined as a set of spectrum-compatible earthquakes at the ground surface level. The normal bilinear rule is adopted as the story shear force-interstory drift relationship. It is shown that the introduction of an equivalent linear model and application of the hybrid inverse eigenmode problem, due to the present author, to this equivalent linear model enable one to construct a new efficient ductility design method for an elastically supported shear building model. This design method, although approximate, does neither require any eigenvalue analysis nor any repetitive procedure including elastic-plastic time-history response analysis. The validity and accuracy of this design method is demonstrated by elastic-plastic time-history response analysis.