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A new non-parametric procedure is presented for extracting seismic fragility curves by considering frequency content of real ground motion records. The implemented non-parametric method is based on parametric methods averaging and clustering the input data based on an intensity measure (IM) using K-means clustering method. As an advantage, it can considerably decrease the number of analyses via an optimization process and using Monte Carlo procedure. The proposed method's accuracy is evaluated for real ground motion records. Results show that although the random selection of records among different clusters can be effective for synthetic records, but it's not suitable for selecting the real ones and can lead to large errors in estimations. Therefore, a classification procedure based on frequency content of the records is used in this study to select an appropriate set of real ground motion records for providing the required IM observations in the method. Then, a set of 472 real ground motion records corresponding to 60 earthquakes is chosen as input data for extracting the fragility curves of the case study structure for evaluating the accuracy and applicability of the non-parametric method. Mean period ( T m ) of the ground motions is considered as a suitable frequency content measure to classify the real ground motion records while this classification can lead to better and more accurate results rather than the Monte Carlo procedure. According to the results, with using the classification procedure, the optimized non-parametric method may require less than 70 nonlinear analyses to extract the fragility curves. [ABSTRACT FROM AUTHOR]

Seismic microzoning at a local scale of a given site or at a global scale of an urban center requires a fairly detailed knowledge of the lateral variations of the site effects, such as the amplification level, the fundamental soil frequency, and the site classification according to a given design seismic code. Over the last decade, the horizontal-to-vertical spectral ratio of background noise has become a widely used tool. However, it still has some shortcomings related to the windows selection as the microtremor contains many unknown and random sources other than the one related to the site effect. In this contribution, one proposes a new approach based on the frequency content to discriminate between the different sources. Site classification scheme recently proposed for seismic accelerations, which define target numerical and analytical horizontal over vertical spectral ratios for the 4 standard soil classes (Rock, soft rock, stiff soil and soft soil) defined in Eurocode-8, is adapted to background noise. In order to test the reliability of the proposed approach, microtremor measurements were performed on 67 sites with available shear-wave velocities down to a depth of at least 30 m. Free-field microtremor measurements are converted to accelerations instead to velocities, and split into 5 s non-overlapping windows. Automatic computation based statistical approach using a classification index which measures the similarity between the measured and target horizontal over vertical spectral ratios is performed for the 67 sites. The obtained results reveal a similar site classification, using the time-averaged shear-wave velocity to 30 m depth (Vs30) and the new approach, which can reach a success rate of about 84%. The automatic calculation provides the 67 sites with two fundamental parameters required for the preparation of a first-order microzonation map, the fundamental soil frequency, and the classification of the site according to Eurocode-8 guidelines. The proposed approach can be very useful for large-scale seismic micro-zoning of urban centers that may involve hundreds of measurement points, or supplement other geophysical measurements for a site specific seismic analysis. [ABSTRACT FROM AUTHOR]

The economic benefits of utilizing numerical simulations versus experimental approaches in geotechnical studies have made them viable tools for engineering assessments. Within this framework, the damages due to earthquake-induced forces and displacements in liquefied ground are amongst the phenomena investigated by many researchers. In the current study, numerical simulation of mildly-sloping liquefied ground under dynamic loading is conducted by the graphical user interface OpenSeesPL, which uses the open-source computational platform OpenSees. Pile-pinning lateral displacement mitigation method in saturated sand is modeled and the effects of artificial earthquake time histories covering a range of different durations and frequency contents on the system response are scrutinized. It is observed that duration and frequency content of the earthquakes changed the initiation time of large deformations. Higher pore pressures were generated in low frequency systems and larger lateral displacements of the improved ground with loose soil were countered with lower accelerations due to the liquefied ground isolating effects. The reliability of different intensity measures for enabling seismic performance assessments are discussed and finally, recommendations for practical hazard evaluations are made. [ABSTRACT FROM AUTHOR]