Damage Index for structures with elements of high flexural stiffness and/or brittle behavior

Structures with high lateral stiffness and/or with brittle to semi-brittle elements in their lateral resistant system may exhibit a rapid decrease of their shear capacity and a sudden loss of stiffness when lateral cyclic loads, as those produced by earthquakes, are applied. This behavior can be related to damage (partial or complete) of a particular structural element. In this article, the expected seismic damage is analyzed and assessed in two different structures. The first one is a low-rise reinforced masonry structure, with hollow concrete blocks (2 stories); the second one is a high-rise dual reinforced concrete building (18 stories). In both cases, materials are characterized using a proper hysteresis model, which takes into account softening and shear degradation. To quantify the structural damage, the well-known Park and Ang damage index is used. The damage curves shown in this paper, exhibit a quick damage increase for relatively low-intensity values, which is attributed to nonlinear incursions of several structural elements with low ultimate ductility. However, incremental dynamic analyses are time-consuming; therefore, it becomes important to develop simplified methods, also successfully representing this kind of effects. A recently proposed damage index, which can be computed in an easy and straightforward way from capacity curves or capacity spectra, is modified in this work to include this fast strength degradation. Details of the computations of this new damage index are also described here.This research has been partially funded by the Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad-MINECO) of the Spanish Government and by the European Regional Development Fund (Fondo Europeo de Desarrollo Regional-FEDER) of the European Union (UE) through projects referenced as: CGL2011-23621 and CGL2015-65913-P (MINECO/FEDER, UE). Mr. Juan Jiménez Pacheco, sponsored by the University of Cuenca, obtained a scholarship from the Ministry of Higher Education, Science and Technology, SENESCYT, Government of Ecuador, for doctoral studies in the Earthquake Engineering program of the UPC-Barcelona Tech.Postprint (published version