Seismic risk and loss estimation for the building stock in Isfahan. Part I: exposure and vulnerability

Abstract

This paper focuses on the exposure and fragility/vulnerability of the residential, mixed residential/commercial, and public building stock of the city of Isfahan, in Central Iran, and constitutes the first part of a seismic risk assessment study for that city. To determine the assets at risk, we first summarize the details of the building stock and population from the available georeferenced 2011 Census data. From this dataset and from a local survey of the city, we categorize the building taxonomy in 27 construction classes characterized by age, height, and material/lateral-load-resisting system. A building exposure model is then assembled by first dividing Isfahan in city blocks and then by assigning the appropriate statistical properties to the buildings, such as construction class, built area, and replacement cost. The population of each city block is also estimated and accounted for. To assess the fragility and vulnerability to earthquake ground motion, for each building class we performed nonlinear dynamic analysis of multiple equivalent single-degree-of-freedom systems. This process generated a set of classand region-specific fragility and vulnerability functions that considered both record-to-record and building-to-building response variability. In the companion paper we used the exposure model and the fragility and vulnerability curves generated for all these asset classes to probabilistically assess the seismic risk of Isfahan.

Seismic Fragility Assessment for a Class of Rc School Buildings in Italy Leveraging Detailed and Reduced-Order Models

“…Lagomarsino and Giovinazzi [30], proposed the relationships to relate macro-seismic and mechanical-based approaches, in which authors provided criteria to trace the SDOF backbone curves for several class of European buildings. Vamvatsikos and Aschheim [31] adopted the paradigm of Performance-Based Design, by means of Yielding Frequency Spectra approach, to define an equivalent SDOF model from a MDOF one, as well as after applied by Kohrangi et al [32] in the vulnerability model for buildings in the municipality of Isfahan, Iran.…”

“…Herein, we are adopting the procedure suggested in [32], by assuming a backbone curve of SDOF models (and the boundary control points for the spring to employ, in terms of θmax vs. F/Fy) according to the seismic behaviour of full MDOF models, given a building taxonomy. With regard to the building taxonomy, it is necessary that both SDOF and MDOF models are belonging to same class, which is defined by the parametrization of at least five parameters, usually available in freely online databases: construction typology (CT), year of construction (CY), number of storeys (NS) and two values among in-plan area (A), total volume (V), interstorey height (Hi) and total height (HTOT).…”

“…To define the SDOF behaviour, the formulation defined in [31] and developed in [32] can be employed, where the parameters of an equivalent SDOF are provided. In particular, given the building taxonomy, the approach consists in the definition of eight parameters and a SDOF backbone shape.…”

“…Three of the eight parameters can be fixed a-priori, as well as the participation factor (Γ) and the mass participation factor (a1) for the first vibration mode and the conventional damping ratio (ξ). For the case at hand, both Γ and a1 can be fixed equal to 1, as suggested in [32]. The remaining three parameters are:…”

“…Firstly, for a class-level purpose, different seismic actions can be considered within the focused area and the definition of the yield spectral acceleration can be differentiated on the basis of the buildings localization. After, some of the eight parameters, such as θy, can be established a-priori on the basis of the CY of the buildings and the reference building code [32]. Nevertheless, the detailed knowledge of the structural behavior of some MDOF structures, representative of the building class, can be used for having a reliable indication about the effective values to employ in the procedure.…”