Statistical assessment of seismic fragility curves for steel jacket platforms considering global dynamic instability

Abstract

ABSTRACTMany probabilistic studies in the field of offshore structures assume that the drift demand distributes lognormally around its median at all the intensity levels. However, this assumption may not be formally validated, and the purpose of this study is to investigate the assumption of lognormal distribution of the drift demand for the fixed offshore platforms, using Anderson–Darling goodness of fit test. The lognormal hypothesis for the drift demand can be investigated at two different regions as: (1) low intensity levels without any collapse case and (2) higher intensity levels with collapse cases. To this end, both the sample median and sample geometric mean are considered as the estimators of lognormal central tendency. The results indicate that the lognormal hypothesise is accepted based on the sample geometric mean at all the intensity levels. Nevertheless, the lognormal hypothesise is rejected at some intensity levels if the sample median is the central estimator.