Earthquake vulnerability of school buildings: Probabilistic structural fragility analyses

The study presents probabilistic structural fragility assessment of public school buildings in Istanbul, which were constructed based on a standardized/typical project. The typical structure is a four-story, reinforced concrete shear wall building with moment resisting frames. Derivation of fragility functions rely on nonlinear dynamic analyses through Monte Carlo simulations. Nonlinear dynamic analyses are initially performed for a fully deterministic structural model based on the blueprints of the typical school building project. Uncertainties are introduced in different analysis cases following a modified version of the algorithm presented in Smyth et al. (2004) [21], which considers the effect of the random distribution of the parameters using a Monte Carlo approach. Aleatory uncertainties concerning material properties (i.e. compressive strength of concrete, yield strength of reinforcing steel and concrete density), geometrical characteristics (i.e. span lengths and story heights) and cross sectional dimensions of beams, columns and shear walls as well as epistemic uncertainty in the direction of ground motion excitation are considered. Statistical distributions for the parameters considered are obtained from in-situ measurements and material sampling tests. Fragility functions are produced in terms of peak ground acceleration and velocity as well as of the elastic spectral displacement at the first vibration period of the building. Mean damage ratios are calculated from the derived fragility functions. They are further compared to mean damage ratios calculated for similar building typologies provided in HAZUS-MH technical manual and in Istanbul building inventory.