Comparing Hysteretic Energy and Ductility Uniform Annual Failure Rate Spectra for Traditional and a Spectral Shape-Based Intensity Measure

Joel Carvajal,Juan Bojórquez,Alfredo Reyes-Salazar,Edén Bojórquez,Sonia Ruiz,Francisco López-Almansa,Ali Rodríguez,Mauro Niño,José Torres,Jorge Ruiz-García,Qian Chen

doi:10.1155/2021/2601087

Joel Carvajal, Juan Bojórquez + Show 9 more

Open Access

https://doi.org/10.1155/2021/2601087

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Abstract

In this study, with the objective to develop a reliability-based seismic design tool, ductility and dissipated hysteretic energy uniform annual failure rate (UAFR) spectra are obtained and compared using the spectral acceleration at first mode of vibration of the structure Sa(T1) and the well-known spectral shape-based intensity measure INp. Notice that this is the first time in the literature that UAFR spectra are obtained for the advanced spectral shape intensity measure INp. For this aim, 110 simulated ground motions recorded from the soft soil of Mexico City were selected due to their large energy amount demanded to the structures; moreover, four elastoplastic hysteretic behavior models are considered for the dynamic analyses with post-yielding stiffness of 0, 3, 5, and 10%. It is observed that the use of elasto-perfectly plastic models provided similar UAFR spectra in comparison with hysteretic models with different post-yielding stiffness. This conclusion is valid for the two selected intensity measures. In addition, the lateral resistance required to achieve similar structural reliability levels is larger when the INp intensity measure is used, especially for buildings with vibration periods equal or larger than the soil period, in such a way that the traditional use of Sa(T1) could provide structures with less structural reliability levels.

Highlights

One of the main features to design structures subjected to earthquakes is the use of design or response spectra. e spectra provided by the seismic regulations are determined in most of the cases through single-degree-of-freedom (SDOF) systems with elastic behavior subjected to a set of seismic records, which are reduced to account for nonlinear behavior via ductility reduction factors. e current version of Mexico City Building Code (MCBC) and most of the codes around the world use the spectral acceleration at first mode of vibration of the structure Sa(T1) to estimate the design lateral resistance and stiffness demand of buildings under earthquakes and to control the maximum lateral displacement demand
Influence of the Hysteretic Energy in the uniform annual failure rate (UAFR) Spectra in terms of the Sa Intensity Measure. e normalized hysteretic energy UAFR spectra when Sa is used as intensity measure for all the models with different post-yielding stiffness under
Ductility and dissipated hysteretic energy UAFR spectra have been computed and compared using spectral acceleration at first mode of vibration and the wellknown INp intensity measures. e results obtained for ductility and hysteretic energy UAFR spectra are as follows

Summary

Introduction

One of the main features to design structures subjected to earthquakes is the use of design or response spectra. e spectra provided by the seismic regulations are determined in most of the cases through single-degree-of-freedom (SDOF) systems with elastic behavior subjected to a set of seismic records, which are reduced to account for nonlinear behavior via ductility reduction factors. e current version of Mexico City Building Code (MCBC) and most of the codes around the world use the spectral acceleration at first mode of vibration of the structure Sa(T1) to estimate the design lateral resistance and stiffness demand of buildings under earthquakes and to control the maximum lateral displacement demand. One of the main features to design structures subjected to earthquakes is the use of design or response spectra. It is known that Sa(T1) presents some limitations when it is used as intensity measure due to its lack of efficiency to predict the nonlinear structural response [1–4]. Sa(T1) does not consider the effect of the elongation of the vibration period when nonlinear behavior occurs. For this reason, Bojorquez and Iervolino [5] proposed a spectral shape parameter named Np and the INp intensity measure toward more efficient parameters. Another two important issues should be accounted for seismic-resistant design of structures. e first one is the inclusion of plastic deformation demands through energy concepts. e use of energy for this purpose was initially discussed by Housner [12]

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Conclusion