RASOR

Risk assessment for the seismic protection of industrial facilities

rasor project website

The main objective of the RASOR project is to develop a systematic PBEE methodology for the seismic risk mitigation of industrial equipment structures, focused on the most important structures of a typical industrial facility: liquid storage tanks, industrial pressure vessels, industrial piping systems and their supports. This objective will be achieved through a multi-disciplinary approach which combines Civil and Mechanical Engineering with Earthquake Engineering, Engineering Seismology, Computational and Stochastic Mechanics, in a effort to produce an integrated seismic risk analysis framework, tailored to the specific characteristics and particularities of industrial installation structures, such as their geometry, high pressure and temperature, operational requirements, material aging and corrosive effects. Of particular importance are the increased safety requirements due the explosive or toxic content of such facilities.

Project Funding

Hellenic General Secretariat for Research and Technology
ESPA 2007-2013, Greek Ministry of Education and Religious Affairs

Collaborators

National Technical University of Athens – NTUA

University of Thessaly – UTh

University of Patras – UPatras

Institute of Engineering Seismology and Earthquake Engineering – ITSAK

Time Period

Jan 2012 – Sep 2015

Relevant Publications

Bakalis K., Kazantzi A.K., Vamvatsikos D., Fragiadakis M. (2019). Seismic performance evaluation of liquid storage tanks using nonlinear static procedures. ASME Journal of Pressure Vessel Technology, 141(1), 010902. DOI:10.1115/1.4039634

Bakalis K., Kazantzi A.K., Vamvatsikos D., Fragiadakis M. (2019). Seismic performance evaluation of liquid storage tanks using nonlinear static procedures. ASME Journal of Pressure Vessel Technology, 141(1), 010902

https://doi.org/10.1115/1.4039634

Abstract | A simplified approach is presented for the seismic performance assessment of liquid storage tanks. The proposed methodology relies on a nonlinear static analysis, in conjunction with suitable “strength ratio-ductility-period” relationships, to derive the associated structural demand for the desired range of seismic intensities. In the absence of available relationships that are deemed fit to represent the nonlinear-elastic response of liquid storage tanks, several incremental dynamic analyses are performed for variable post-yield hardening ratios and periods in order to form a set of data that enables the fitting of the response. Following the identification of common modes of failure such as elephant’s foot buckling (EFB), base plate plastic rotation, and sloshing wave damage, the aforementioned relationships are employed to derive the 16%, 50%, and 84% percentiles for each of the respective response parameters. Fragility curves are extracted for the considered failure modes, taking special care to appropriately quantify both the median and the dispersion of capacity and demand. A comparison with the corresponding results of incremental dynamic analysis (IDA) reveals that the pushover approach offers a reasonable agreement for the majority of failure modes and limit states considered.

Bakalis K., Vamvatsikos D., Fragiadakis M. (2017). Seismic risk assessment of liquid storage tanks via a nonlinear surrogate model. Earthquake Engineering and Structural Dynamics, 46(15): 2851-2868. DOI: 10.1002/eqe.2939

Bakalis K., Vamvatsikos D., Fragiadakis M. (2017). Seismic risk assessment of liquid storage tanks via a nonlinear surrogate model. Earthquake Engineering and Structural Dynamics, 46(15): 2851-2868

https://doi.org/10.1002/eqe.2939

Abstract | A performance‐based earthquake engineering approach is developed for the seismic risk assessment of fixed‐roof atmospheric steel liquid storage tanks. The proposed method is based on a surrogate single‐mass model that consists of elastic beam‐column elements and nonlinear springs. Appropriate component and system‐level damage states are defined, following the identification of commonly observed modes of failure that may occur during an earthquake. Incremental dynamic analysis and simplified cloud are offered as potential approaches to derive the distribution of response parameters given the seismic intensity. A parametric investigation that engages the aforementioned analysis methods is conducted on 3 tanks of varying geometry, considering both anchored and unanchored support conditions. Special attention is paid to the elephant’s foot buckling formation, by offering extensive information on its capacity and demand representation within the seismic risk assessment process. Seismic fragility curves are initially extracted for the component‐level damage states, to compare the effect of each analysis approach on the estimated performance. The subsequent generation of system‐level fragility curves reveals the issue of nonsequential damage states, whereby significant damage may abruptly appear without precursory lighter damage states.

[pre-print version]

Bakalis K., Fragiadakis M., Vamvatsikos D. (2017). Surrogate modeling for the seismic performance assessment of liquid storage tanks. ASCE Journal of Structural Engineering, 143(4): 04016199. DOI: 10.1061/(ASCE)ST.1943-541X.0001667

Bakalis K., Fragiadakis M., Vamvatsikos D. (2017). Surrogate modeling for the seismic performance assessment of liquid storage tanks. ASCE Journal of Structural Engineering, 143(4): 04016199

https://doi.org/10.1061/(ASCE)ST.1943-541X.0001667

Abstract | A three-dimensional surrogate model is presented for the seismic performance assessment of cylindrical atmospheric liquid storage tanks. The proposed model consists of a concentrated fluid mass attached to a single vertical beam-column element that rests on rigid beam-spokes with edge springs. The model is suitable for rapid static and dynamic seismic performance assessment. Contrary to other simplified models for tanks, its properties are determined through a simple structural analysis that can be performed in any nonlinear analysis software, without the need for complex finite-element models. The results compare favorably to those of three-dimensional finite-element models on three tanks of varying aspect ratios. A step-by-step example of the modeling procedure is presented for a squat unanchored tank, and a sensitivity analysis is conducted in order to investigate the effect of various modeling parameters on the seismic response of the proposed tank model.

[pre-print version]

Bakalis K., Fragiadakis M., Vamvatsikos D. (2015). Seismic fragility assessment of steel liquid storage tanks. Proceedings of the ASME 2015 Pressure Vessels & Piping Conference PVP2015, Boston, MA

Bakalis K., Fragiadakis M., Vamvatsikos D. (2015). Seismic fragility assessment of steel liquid storage tanks. Proceedings of the ASME 2015 Pressure Vessels & Piping Conference PVP2015, Boston, MA

[paper]

Abstract | A seismic fragility assessment procedure is developed for atmospheric steel liquid storage tanks. Appropriate system and component-level damage states are defined by identifying the failure modes that may occur during a strong ground motion. Special attention is paid to the elephant’s foot buckling failure mode, where the estimation of the associated capacity and demand requires thorough consideration within a probabilistic framework. A novel damage state is introduced to existing procedures with respect to the uncontrollable loss of containment scenario. Fragility curves are estimated by introducing both aleatory and epistemic sources of uncertainty, thus providing a comprehensive methodology for the seismic risk assessment of liquid storage tanks. The importance of dynamic buckling is acknowledged and the issue of non-sequential damage states is finally revealed.

Bakalis K., Fragiadakis M., Vamvatsikos D. (2015). Surrogate modelling of liquid storage tanks for seismic performance design and assessment. Proceedings of the COMPDYN2015 Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Crete, Greece

Bakalis K., Fragiadakis M., Vamvatsikos D. (2015). Surrogate modelling of liquid storage tanks for seismic performance design and assessment. Proceedings of the COMPDYN2015 Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Crete, Greece

[paper]

Abstract | The finite element method (FEM) is often employed to create detailed models for the seismic assessment and design of liquid storage tanks. This comprehensive approach offers accuracy, which is counter-balanced however by its computational inefficiency, especially for the case of large-scale engineering problems. Regardless of the continuous evolution of computer technology, surrogate models are necessary when such problems of engineering practice are encountered. This study, attempts to develop an appropriate surrogate modelling approach, tailored for the design and seismic risk assessment of liquid storage tanks. A formulation that disregards fluid-structure-interaction is employed in view of providing a reasonable compromise between modelling complexity and error. At the same time, a simplified methodology based on nonlinear static procedures is proposed for the assessment of atmospheric tanks. The comparison with Incremental Dynamic Analysis reveals a reasonable, yet conservative in some cases, match for the damage states considered, thus offering an alternative methodology that may easily be incorporated within code-based provisions.

RASOR Members

Eirini Vourlakou2022-10-31T14:42:23+02:00

Dimitrios VAMVATSIKOS

Eirini Vourlakou2024-11-19T15:50:18+02:00

Konstantinos BAKALIS