THE RELATION BETWEEN LOCAL AND OVERALL DUCTILITY DEMANDS IN MULTI-DEGREE OF FREEDOM, FRAMED TYPE STRUCTURES

Strong earthquakes cause inelastic behavior in most of structures resulting in increased deformations and a reduction in member forces In some period ranges. The force reduction coefficient for single degree of freedom (SDOF) systems can easily be defined and related to the deformation ( ductility ratio ). However for multi-degree-of-freedom (MDOF) systems and real structures the relation between ductilities and for reduction coefficients is not clear. The exact average elastic and inelastic response spectra of SDOF system due to ten selected earthquake records are computed. Shear beam models representing framed type structures with selected stories are considered and the elastic and inelastic response spectra of these system, for assumed deformation ductilities, due ۱۰ those earthquake records are computed and presented. The response spectra of each model are compared with those of SDOF systems. The ratio of elastic to inelastic spectra are compared with Newmark's rules for different ductility level.