Analytical Fragility Curves for Pipe Rack Structure

The seismic performance of Pipe Rack structures which is a complex structure commonly found in large oil refineries is evaluated in this study. Analytical Fragility curves are developed to evaluate the performance of each pipe rack models at Life Safety damage state after an earthquake. The methodology that were used to develop the curves, are based on calculating axial deformation of the brace member and the plastic rotation of the moment frame using nonlinear time history analysis for different ground motions with different intensities and frequency contents. The fragility curves are developed based on the acceptance criteria for the brace member and the partially connection moment frame given from the FEMA 356. It was found that as the number of bay increased, the probability of the structure exceeding/reaching Life Safety performance level for the brace member significantly increased and decreased as the number of bay decreased. Similarly, as the number of stories increase, the chance of reaching LS increased, as decreasing the number of stories lowered the change of achieving LS for both moment frame and brace member. It was also found that changing the member size does not have a remarkable effect to their fragility values in Life Safety level of performance.