Fragility Assessment of Floating Roof Storage Tanks during Severe Rainfall Events
Publication: Journal of Performance of Constructed Facilities
Volume 34, Issue 6
Abstract
In 2017, Hurricane Harvey, highlighted the vulnerability of floating roof storage tanks to severe rainfall events. Several floating roofs failed due to rainwater accumulating on them, causing the release of hundreds of tons of pollutants in the atmosphere. Despite the vulnerability of floating roofs, tools currently are lacking to evaluate their anticipated performance during rainstorms. This paper presents the development and application of fragility models to assess the vulnerability of floating roofs subjected to rainwater loads and help prevent future failures. First, a finite-element model of floating roofs and a load-updating method are presented to assess the potential for failure. By coupling the finite-element model with a statistical sampling method, fragility models were derived for two damage mechanisms: sinking of the roof, and excessive stresses due to the rainwater weight. Fragility models were developed for undamaged roofs and roofs with pre-existing damage (i.e., punctured pontoons). To allow their use for future or historic rainfall events, a framework is presented to estimate the maximum amount of rainwater standing on a roof and the probability of failure during a rainstorm. Lastly, forensic investigations of a floating roof failure that occurred during Hurricane Harvey were performed to illustrate the viability of the fragility models to understand the conditions leading to failures and to propose mitigation measures. Insights from the fragility analysis indicate that small floating roofs are more vulnerable to rainwater loads than are large roofs, whereas insights from the failure investigation reveal the importance of efficient roof drainage, as well as terrain drainage to prevent water accumulation around the storage tank, which can lead to inefficient roof drains. Results also indicate that in preparation for a rainstorm, storage tanks should be filled with product to improve floating roof drainage.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request (e.g., floating roof finite-element model; and MATLAB code for the load-updating method, to generate Latin hypercube samples, to develop fragility models, and to estimate the amount of accumulated rainwater on a roof).
Acknowledgments
The authors acknowledge the support of this research by the National Science Foundation under award No. CMMI-1635784. The contributions of the first author were supported in part by the Natural Sciences and Engineering Research Council of Canada and the Rice University Nettie S. Autrey Fellowship. Any opinions, findings, and conclusions or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the sponsors.
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Published In
Journal of Performance of Constructed Facilities
Volume 34 • Issue 6 • December 2020
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Jun 13, 2019
Accepted: May 27, 2020
Published online: Aug 19, 2020
Published in print: Dec 1, 2020
Discussion open until: Jan 19, 2021
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