Fragility curves is a statistical tool representing the probability of exceeding a given damage state (or performance) as a function of an engineering demand parameter that represents the ground motion (preferably spectral displacement at a given frequency Hence, fragility curves are nothing but finding out the vulnerability of building. It is the graph of peak ground acceleration(PGA on X axis) and % of damage on Y axis.
What is the concept of fragility curve?. Available from: https://www.researchgate.net/post/What_is_the_concept_of_fragility_curve [accessed May 29, 2017]