Development of Fragility Curves for an RC Frame

Fragility curves provide the conditional probability of structural response when subjected to earthquake loads as a function of ground motion intensity or other design parameters. Seismic fragility curves are used mainly by decision makers for the assessment of seismic losses both for pre-earthquake disaster planning as well as post-earthquake recovery programs. Generation of fragility curves in conventional methods involves development of large number of computational models that represent the inherent variation in the material properties of particular building type and its earthquake time history analyses to obtain an accurate and reliable estimate of the probability of exceedance of the chosen damage parameter. There are many Response surface methods available in the literature that is capable of representing the limit state surface depending on the problem type. High Dimensional Model Representation (HDMR) method is a type of response surface method that can express input-output relations of complex computational models. This input-output relation can reduce the number of iterations of expensive computations especially in problems like fragility curve development. Unnikrishnan et al. (2012) applied this technique in fragility evaluation for the first time and demonstrated its computational efficiency compared to computationally intensive Monte Carlo method. In this study, fragility curve of an RC frame is developed using HDMR response surface method. There are also other simplified approaches which are computationally easy for fragility curve development. Cornell et.al. (2002) proposed such a simplified method which assumes a power law model between the damage parameter and intensity measure of earthquake. This study presents Fragility curves evaluated using HDMR and its computational efficiency with reference to the one using the method suggested by Cornell et al (2002)