Action 6.4 : Seismic Risk assessment in Intensity domain and Case study

State of the art / Background knowledge

The actual practice of seismic risk assessment for nuclear power plants is based on Uniform Hazard Spectra (UHS) derived from Probabilistic Seismic Hazard Assessment (PSHA) [1] in the format of (pseudo) spectral accelerations. The spectral (force-based) method is still widely applied in earthquake engineering, especially in the design of systems. It is also applied in fragility analysis [2]. This methodology has the problem that UHS in reality do not represent a uniform hazard but the weighted contribution of earthquakes leading to very different intensities at the plant site.

Limitations of current practice or knowledge (i.e. technological barrier)

Different intensities mean different damaging impact of the underlying earthquakes. From a physical point of view, this difference is rather obvious. For causing damage and destroying something, it is necessary to perform work. For this, it is necessary to provide the corresponding seismic energy that acts on SSCs over a certain period. A uniform hazard spectrum in terms of spectral accelerations does not provide this information. Therefore, the information on the true damaging characteristics of the earthquakes contributing to the UHS is lost.

Using mathematical deaggregation methods it is possible to define a controlling earthquake in terms of magnitude, distance to the site and ε – the number of standard deviations of aleatory variability corresponding to the selected (or weighted by a logic tree) median empirical ground motion prediction equation. The site intensity defined by the characteristics of the controlling earthquake can be defined, for example, by using a regionally validated intensity attenuation equation.

Based on empirical information (registered time-histories) or by waveform modeling it is possible to define ground motion acceleration time-histories that correspond to the site intensity, capturing at the same time the range of uncertainty associated with the different registrations of earthquakes matching the same intensity.

Fig6 4

 Figure 1:Registered time-histories for site intensity VII
                (example, European-Mediterranean Seismological Center, 2013,
                “Resorce Reference Database for Seismic Ground-Motion in Europe”,
                EMSC France)

Program of research

The work can be subdivided into the following subprojects :

1. Develop a methodology for selecting intensity (EMS-98) compatible time-histories from available databases taking into account site classification (EUROCODE). Prepare a database of quality assured time histories for moderate earthquakes (intensity VI-VII (VIII)).

2. Develop a methodology for calibrating time-histories derived by waveform modeling against site intensities. Calibration process will be based on structural dynamic nonlinear or equivalent linear-elastic analyses of standardized buildings of a predefined vulnerability class with codes like SC SASSI or LS DYNA (or equivalent codes). For waveform modeling, methods like synthetic seismograms or kinematic source modeling will be applied. Develop a database of generated time-histories for intensities VIII-X taking into account site classification (EUROCODE).

3. Develop a methodology for defining intensity-compatible fragility functions for structures, systems and components from tests using time-histories developed in subprojects 1 and 2.

4. Develop an experimental case study using the SMART (Seismic design and best-estimate Methods Assessment for Reinforced concrete buildings subjected to Torsion and non-linear effects) building (www.smart2013.eu). The objective is to test all parameters developed in the others tasks and/or WPs (ex CAV, CMS, CS, RVT….)   

                                                                                                                                                                   

Organization

  • Type: PhD
  • Collaboration: in progress
  • Status: Not started yet

Supporting Literature

Klügel, J.U.; Stäuble Akcay, S.: Development of intensity compatible time-histories for dynamic analysis of buildings 16 WCEE, 2017, Santiago Chile, Paper No 4894

Klügel, J.-U.; Stäuble Akcay, S. : Towards damage-consistent performance-based design of critical infrastructures -2017 (ERES 2017, July 2017 in Int. Journal of Computational Methods and Experimental Methods (2017)

Klügel, J.U. : Damage-consistent hazard assessment – the revival of intensities, EGU, General Assembly Meeting, 2016, Poster Presentation, Natural Hazards, Track 4.6

Klügel, J.U. : Understanding site-specific PSHA results by hazard deaggregation into site intensities, EGU, General Assembly Meeting, 2016, Poster Presentation, Natural Hazards, Track 4.6