Investigation of the Effect of the Ground Motion Characteristics on the Ry-μ Relation for the Inelastic Response of SDOF Structures

Abstract eng:
In this study, the effect of the ground motion frequency content, especially the period of the directivity pulse in near field records, on the relationship between the reduction factor Ry and the ductility demand µ is investigated. A large sample of strong motion records showing near field characteristics of forward and backward directivity, is examined. The regimes, in which the known assumptions of equal displacement and equal energy are valid, are re-evaluated taking into account the period of the directivity pulse contained in the ground motion. The results show that, for near field records with directivity effects, the thresholds of these regions depend on the period of the directivity pulse, which is related to the magnitude of the earthquake. This observation is valid for ground motions with intense and weak forward directivity and backward directivity effects. This response implies that the equal displacement rule (Ry=µ), which is incorporated in most earthquake design regulations for structures with a period larger than Tc, with Tc being the threshold between the constant acceleration and the constant velocity regions on the response spectrum, might underestimate significantly the ductility demand for structures with long periods. In this analysis, a new method for deriving the pulse duration in case of weak forward and for backward directivities is proposed and a new limit for the regime, in which the equal displacement assumption applies, is defined.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket