Research challenges

A systematic seismic risk methodology for industrial equipment structures will be developed in the course of the proposed research. To assess the capacity of industrial equipment structures, numerical methodologies and algorithms will be developed and implemented, based on the extensive experience of the involved partners, necessitating the collaboration between researchers from different disciplines (Civil and Mechanical Engineering, Earthquake Engineering, Engineering Seismology, Computational and Stochastic Mechanics).

More specifically, the following scientific challenges will be faced:

• Generation of correlated ground motion records, accounting for basin-edge-generated surface waves, as well as for asynchronous ground motions in structures with large footprints based on a stochastic approach. Seismic records from Greece will be used to determine the source spectra scaling law. In addition, the Specific Barrier Model will be calibrated to typical Greek site conditions, whereas seismic attenuation data will be selected and evaluated in terms of local conditions. The above seismological research will result in the development of appropriate time histories and design spectra, to be used for Probabilistic Seismic Hazard Analysis of industrial equipment structures. 

• Development of both rigorous and simplified numerical models for the nonlinear seismic analysis of industrial equipment structures. The models will be capable to predict all possible damage modes, and account for liquid-structure interaction including the effects of foundation flexibility. These are open research topics since many relevant aspects are treated rather empirically in current design practice. Modeling issues that require further research investigation are: (a) uplifting of unanchored tanks and base plate failure; (b) floating roof behavior; (c) nonlinear sloshing effects; (d) influence of uncertainties (initial geometric imperfections, material degradation); (e) response under strong cyclic loading in pressure vessel and piping components (damage accumulation and low-cycle fatigue).

• Development of computationally efficient methodologies for seismic risk-assessment of industrial equipment structures. First, simple and efficient methodologies, which require a small number of analyses/simulations, will be developed. Subsequently, more rigorous methodologies based on synthetic ground motions will be developed for producing benchmark results. Thus different simplified risk-assessment methodologies will be evaluated to establish a hierarchy of methods that achieve different compromises between computational efficiency and accuracy.

The overall objective of the proposed research is the integration of the above partial objectives, into a general performance-based design and seismic risk analysis framework for key industrial equipment structures. This is an ambitious goal of significant importance for the safety of the population and the protection of the environment, as well as for the economy and the sustainable growth by ensuring the unhindered supply of strategic resources.