Seismic Vulnerability Assessment of School Buildings in Mexico

Abstract eng:
In this paper criteria for seismic vulnerability assessment of school buildings in Mexico are presented. The criteria consider the estimation of non-linear responses using structural models. Some dynamic properties of those models are calibrated from experimental analysis considering ambient vibration records. For describing the seismic vulnerability we use two different criteria, i) based on reliability functions that consider the Secant Stiffness Reduction Index (SSRI) and ii) based on reliabilty functions using SSRI and Simplified Reference Systems (SRS). These criteria were implemented in a school building that belongs to UPAEP University infraestructure. To determine the SSRI it is necessary to carry out the pseudo-static non-linear response (pushover analysis) of the structural model that corresponds to a multiple degrees of freedom system. From this analysis we obtain a curve that relates the shear base, V b , with the global lateral displacement at the roof of the system, X N . Apart from these curves, the pushover analysis provides a series of lateral configurations of the displacements in different levels and response values at each instant of interest. Pushover analysis also provides the estimation of the deterministic deformation capacity, uF, of the structural system. In this paper the criterion for estimating the deformation capacity corresponds to a 20% reduction of the peak shear value. The pushover analysis is useful to obtain the mechanical properties of SRS. The non-linear analysis also includes the response estimation obtained from step by step procedures of the same structural models described in above section; we also considered the uncertainties in the structural properties and for different seismic excitations. For this analysis a modified version of DRAIN-2D software is used. If we have a representative sample of the resulting responses, we can determine the probability distribution of the response; such distribution is characterized by the expected value of response and the corresponding interval in terms of seismic intensity. In order to estimate the structural reliability function, a probabilistic model of the mechanical properties and the gravitational loads acting on the system can be formulated. The reliability functions mentioned in criteria ii and iii) are in terms of Cornell´s reliability index, and here we use a normalized seismic intensity measure. In order to illustrate the procedures a case was analysed that corresponds to reinforced concrete school building located in central Mexico. Finally, the seismic vulnerability assessment can be useful for estimating the seismic risk level and for the establishment of the rehabilitation strategies of those buildings.

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