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Seismic reliability procedures and input ground-motions for nonlinear dynamic analyses

Keywords: earthquake engineering, accelerograms, intensity measures, nonlinear dynamic analysis, seismic hazard
Fig. 1. IDA curves calibrated for a given seismic intensity measure (Bianchini).
Fig. 2. Selection of recorded accelerograms (Buratti).
Fig. 3. Fragility curves obtained from response surface models (Buratti).

In the framework of Performance-Based Earthquake Engineering the actual research trend is to develop rigorous probabilistic approaches. These latter involve complex nonlinear problems with many random and non-random variables. For this reason many practical reliability methods have been recently developed. The research carried out by the group is mainly focused on the extension two of these approaches: the “2000 SAC/FEMA Method” and responsesurface based methods. The 2000 SAC/FEMA Method was applied to analyse the reliabiliy of R.C. frames with and without dampers. Response- surfaces with random factors are statistical models used for approximating seismic capacity with computational efficiency. A proper selection criterion for the accelerograms is crucial for the correct prediction of structural response. The research group developed a new probabilistic seismic hazard analysis (PSHA) procedure. Using this results the group developed a new vector ground-motion intensity measure based on the combination of PGA and PGV and proposed a ground-motion selection criterion based on this parameter. The research group also developed procedures for simulating non-stationary stochastic accelerograms. The so generated accelerograms were used as input for nonlinear dynamic analyses of various RC structures and gave results that compared very well with those obtained from recorded accelerograms. Particular care was put into the study of the sensitivity of the results to the groundmotion intensity measure used. This issue was further investigated during a collaboration with the “Blume Earthquake Engineering Center” at Stanford University, that lead to the proposal to a new intensity measure. Finally, as a results of a collaboration with Imperial College, London, the research group developed a new criterion to select and scale recorded accelerograms starting from the definition of a scenario in terms of magnitude and source-to-site distance. The procedure is based on the definition of a target response spectra, using the data provided by spectral- acceleration attenuation relationships.

Main publications

Palermo, M., Silvestri, S., Gasparini, G., & Trombetti, T. (2014). A statistical study on the peak ground parameters and amplification factors for an updated design displacement spectrum and a criterion for the selection of recorded ground motions. Engineering Structures, 76, 163-176.

Buratti N., Stafford P.J., Bommer J.J. (2011) Earthquake accelerogram selection and scaling procedures for estimating the distribution of structural response. Journal of Structural Engineering 137, 345-157.

Buratti N., Ferracuti B., Savoia M. (2010). Response Surface with random factors for seismic fragility of reinforced concrete frames. Structural Safety. vol. 32, pp. 42 - 51 ISSN: 0167-4730.

Landi L., Vorabbi C., Diotallevvi P.P. (2015) Correlation between the probabilistic seismic asssment of frame structures without and with added dampers. COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. Crete, 25-27 May.

Landi L., Fabbri O. and Diotallevi PP (2013). Simplified method for the assessment of the nonlinear seismic response of structures equipped with viscous dampers. Proceedings of the 11th International Conference on Structural Safety & Reliability, Columbia University, NY, USA.

Buratti N. (2012) A comparison of the performances of various ground–motion intensity measures. 15th World Conference on Earthquake Engineering. Lisbon, 24-28 September.

Ligabue V., Buratti N. (2012) Analysis of codebased ground-motion selection procedures in terms of inelastic interstorey drift demands. 15th World Conference on Earthquake Engineering. Lisbon, 24-28 September.

Buratti N., Savoia M. (2010). Artificial Nonstationary Accelerograms with Natural Variability. XIV European Conference on Earthquake Engineering. Ohrid, Republic of Macedonia. 30 August - 3 September.

Bianchini M., Diotallevi P.P., Landi L (2010). Seismic reliability assessment of RC structures based on different ground motion prediction models. XIV European Conference on Earthquake Engineering. Ohrid, Republic of Macedonia, 30 August – 3 September .

Bianchini M., Diotallevi P.P., Baker J.W. (2009). Prediction of inelastic structural response using an average of spectral accelerations. X International Conference on Structural Safety and Reliability (ICOSSAR). Osaka, Japan, September 13- 17.

Bianchini M., Diotallevi P.P., Landi L.. (2008). Influence of earthquake intensity measure on the probabilistic evaluation of RC buildings. XVI World Conference on Earthquake Engineering (WCEE). Beijing, China, 12-17 October.

Bianchini M., Diotallevi P.P., Landi L. (2007). Full probabilistic approach for seismic reliability assessment of RC frames structures. X International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP). Tokyo, Japan, 31 July-3 August .

Trombetti T., Ceccoli C., Silvestri S., Gasparini G. (2003). Probability Density Function of the Peak Ground Acceleration due to the Seismic Action. Proceedings of the 9th International Conference on Applications of Statistics and Probability in Civil Engineering - ICASP 9. San Francisco. California, 6-9 July.

Trombetti T., Gasparini G., Silvestri S. (2004) Statistical characterisation of the seismic action (PGA and PGV) for Performance Based Seismic Design, Proceedings of the 13th World Conference on Earthquake Engineering. Vancouver, B.C., Canada, 1-6 August.

Trombetti T., Silvestri S., Gasparini G. (2009). The Role Of Epsilon For The Identification Of Groups Of Earthquake Inputs Of Given Hazard. Proceedings of 10th International Conference on Structural Safety and Reliability. Osaka, Japan, 13-17 September.

Silvestri S., Trombetti T., Gasparini G. (2009) A Procedure For Probabilistic Seismic Hazard Analysis Which Allows To Account For Poisson Or Non-Poissonian Models. Proceedings of 10th International Conference on Structural Safety and Reliability. Osaka, Japan, 13-17 September.