Turkey-Adjusted NGA-W1 Horizontal Ground Motion Prediction Models

The objective of this paper is to evaluate the differences between the Next Generation Attenuation: West-1 (NGA-W1) ground motion prediction models (GMPEs) and Turkish strong ground motion dataset and to modify the required pieces of the NGA-W1 models for applicability in Turkey. A comparison dataset is compiled by including strong motions from earthquakes occurred in Turkey and earthquake metadata of ground motions consistent with the NGA-W1 database. Random-effects regression is employed and plots of the residuals are used to evaluate the differences in the magnitude, distance, and site amplification scaling. Incompatibilities between the NGA-W1 GMPEs and Turkish dataset in small-to-moderate magnitude, large distance and site effects scaling are encountered. The NGA-W1 GMPEs are modified for the misfit between the actual ground motions and the model predictions using adjustments functions. Turkey-Adjusted NGA-W1 models are compatible with the regional strong ground motion characteristics and preserve the well-constrained features of the global models.

Comparison of the NGA-W1 Vertical-to-Horizontal Spectral Acceleration Ratio Prediction Equations with Turkish Strong Ground Motion Database

Ground motion prediction models for the vertical-to-horizontal spectral acceleration (V/H) ratio were developed recently by Gulerce and Abrahamson (2011) using NGA-W1 database. Turkish strong ground motions may show a divergence from the V/H ratio model predictions, since only six earthquakes occurred in Turkey were included in the database. A strong motion dataset consistent with the V/H ratio model parameters is developed by including strong motion data from earthquakes occurred in Turkey with at least three recordings per earthquake. The objective of this study was to evaluate the compatibility of V/H ratio prediction model with magnitude, distance, and site amplification scaling of the Turkish ground motion dataset. No significant trend is observed in the model residual with respect to magnitude, rupture distance, and V s30 plots within the applicability range of the prediction model. Analysis results indicate that Gulerce and Abrahamson (2011) model is a suitable candidate model for probabilistic seismic hazard assessment studies in Turkey.

Comparison of field loading test results of bored piles with bearing capacity analysis based on various standards

ICA Construction (Ictas ‐ Astaldi JV) is the general contractor of the WHSD ring road project in St. Petersburg and Section 7 & 8 of M11 Motorway project, which will be the toll highway between St. Petersburg and Moscow. WHSD ring road that has been constructed by ICA Construction passes through nearshore and offshore areas on viaducts and there are also two cable stayed bridges on the alignment. As a part of M11 motorway project, several bridges have been constructed overpassing various rivers. Since, all these structures have deep foundation systems, several axial pile loading tests have been performed on both projects. Soil in the vicinity of St. Petersburg consists of soft to medium dense silty, partially sandy clay layers at top levels. These layers are followed by Cambrian aged hard clay layers. In Russian Federation and some Eastern European countries, bored pile design is based on SNIP norms. In norms like AASHTO or Eurocode, pile bearing capacity calculations consider both contribution of the tip resistance and skin friction. On the contrary, in SNIP norms contribution of the skin friction to pile bearing capacity is very limited. Therefore, piles are generally extended to deep bearing layers. For piles where large axial bearing capacities are required, base enlargement is applied. In this paper, axial pile bearing capacities in the scope of the above mentioned projects are calculated based on SNIP, AASHTO LRFD and Eurocode 7, respectively and the calculated values are compared with the pile bearing capacities obtained from field tests. Total number of axial pile load tests gives the possibility to make a statistical comparison. Results of axial pile load tests have revealed that especially the bearing capacities calculated in accordance with SNIP norms underestimates bearing capacities of bored piles erected in clayey soils.

Turkey-Adjusted Next Generation Attenuation Models

The objective of this study is to evaluate the regional differences between the worldwide based NGA-W1 ground motion models and available Turkish strong ground motion dataset and make the required adjustments in the NGA-W1 models. A strong motion dataset using parameters consistent with the NGA ground motion models is developed by including strong motion data from Turkey. Average horizontal component ground motion is computed for response spectral values at all available periods using the GMRotI50 definition consistent with the NGA-W1 models. A random-effects regression with a constant term only is used to evaluate the systematic differences in the average level of shaking. Plots of residuals are used to evaluate the differences in the magnitude, distance, and site amplification scaling between the Turkish dataset and the NGA-W1 models. Model residuals indicated that the ground motions are overestimated by all 5 NGA-W1 models significantly, especially for small-to-moderate magnitude earthquakes. Model residuals relative to distance measures plots suggest that NGA-W1 models slightly underestimates the ground motions for rupture distances within 100-200 km range. Models including the aftershocks over-predict the ground motions at stiff soil/engineering rock sites. The misfit between the actual data and model predictions are corrected with adjustments functions for each scaling term. 

Turkey-Adjusted NGA-W1 models proposed in this study are compatible with the Turkish strong ground motion characteristics and preserve the wellconstrained features of the global models. Therefore these models are suitable candidates for ground motion characterization and PSHA studies conducted in Turkey.