Cumulative Damage of Degrading Structures Due to Soft Soil Seismic Sequences

Abstract

Several studies have attributed to cumulative damage as the origin of the collapse of tens of buildings in Mexico City during the strong September 19, 2017 (Mw7.1) earthquake. However, some of the previous studies based their conclusions on results from nondegrading elastoplastic or only-stiffness degrading single-degree-of-freedom, SDOF, systems. Therefore, an examination of cumulative damage of buildings having degrading (i.e., stiffness-and-strength degradation) global behavior is pertinent. From the results of this investigation, it is shown that the evolution of normalized hysteretic energy, NHE, which is closely related to the cumulative damage, strongly depends on the hysteretic features and the yield strength coefficient of the system as well as the relationship between its period of vibration and the predominant period of the ground motion. Furthermore, energy-based damage assessment should be carried out with analytical models that include degrading stiffness-and-strength hysteretic features and post-peak negative slope rather than using nondegrading hysteretic features. Finally, it was shown that cumulative damage is negligible between the strong 1985 and 2017 earthquakes for the case-study buildings at two distinct soft soil sites in Mexico City.