Visit in RESSLab of Konstantinos Bakalis

Abstract

Large-capacity atmospheric tanks are widely used to store a variety of liquid-form materials that are deemed necessary for the functionality of any modern community. The devastating consequences of earthquake damage on liquid storage tanks (e.g. Kocaeli 1999, Tohoku 2011) have revealed the vulnerability of such structural systems against strong ground motions, while at the same time have highlighted the need for innovative engineering concepts in order to mitigate the associated socioeconomic losses. Along these lines, the seismic performance of industrial-facility atmospheric liquid storage tanks is examined, in view of providing an easy-to-implement assessment tool that offers reliable results within a reasonable timeframe with respect to structural analysis as well as the associated post-processing.

Following the concepts of performance-based earthquake engineering, a three-dimensional surrogate model is formed to obtain the distribution of the various engineering demand parameters of interest under earthquake loading. Liberated from the need for structure-specific calibration using detailed finite element models, the proposed model is able to represent both anchored and unanchored liquid storage tanks, using ground motion components at multiple principal loading directions simultaneously. Exploiting the virtues of the model in our disposal allows to summarise a considerable volume of analysis results in the form of the fragility curves and perform the subsequent integration with the site hazard of interest to derive the associated mean annual frequency of exceeding certain failure mode thresholds.

In view of a comprehensive seismic risk assessment estimation, both component and system-level damage states are employed. Commonly observed modes of failure such as base plate plastic rotation, elephant’s foot buckling, sloshing-wave-induced damage and anchorage failure, are used to form the component-level damage classification. Special attention is paid to the elephant’s foot buckling failure mode, as the underlying criterion to signal failure is time and seismic intensity dependent. The aforementioned failure modes are appropriately combined to form the system-level damage classification and thus obtain information for a group of tanks rather than a structural system alone.

Bio

Konstantinos was born in Larissa, Greece in 1986. He holds a Degree in Civil Engineering from the Aristotle University of Thessaloniki (2010) and an MSc with merit in Earthquake Engineering with Disaster Management from the University College London (2011). Following the completion of his MSc studies, he worked as a Discipline Engineer for a UK oil & gas engineering consultancy (DeepSea UK) joining the Subsea Structures group. Since June 2013 he has joined the Institute of Steel Structures at the National Technical University of Athens, where he obtained his PhD (2018). His research is focused on the seismic performance assessment of industrial facility liquid storage tanks, using nonlinear static and dynamic methods as well as probabilistic concepts for the performance evaluation under earthquake excitation. He has also participated in several national and international research projects, funded by the EU Research Executive Agency, the EU Research Fund for Coal and Steel and the Hellenic General Secretariat for Research and Technology.