Effects of Degrading Models for Ductility and Dissipated Hysteretic Energy in Uniform Annual Failure Rate Spectra

Abstract eng:
One of the most important tools for seismic design purposes is the response spectrum because it represents the maximum demands on structures. Nevertheless, two aspects should be included on seismic response spectra provided by codes. The first aspect is the inclusion of specific reliability levels on the structures designed. The second is the inclusion of cumulative demands through plastic deformation. While uniform annual failure rate (UAFR) spectra can be used to account for the structural reliability, cumulative demand can be accounted through dissipated hysteretic energy spectra. In this paper the effects of degrading models for ductility and dissipated hysteretic energy UAFR spectra are studied. Narrow-band motions from the soft soil of the valley of Mexico were selected due to the large energy amount that demands to the structures. The implications to use simplify models as the well-known elasto-plastic to obtain the requirements of lateral strength are analyzed. Especially, the larges differences on the seismic coefficient obtained through simplify hysteretic models and degrading models are discussed. It is observed in structures that exhibit low to moderate degradation in strength, and low degradation in stiffness that the use of simplify hysteretic models can be adequate. However, with the aim to obtain satisfactory designs, for structures with important levels of degradation in stiffness, constitutive laws to represent with good accuracy the hysteretic behavior of structures are necessaries in the design spectra, or specific factors to account for the degradation in the mechanical characteristics.

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