Quantitative calibration of two-dimensional aggravation factors in the seismic response of basins: a work-in-progress approach using OpenSees and Python

The quantitative prediction of the seismic response of basins is difficult to achieve due to the highly two- and three-dimensional phenomena involved. Eurocode 8 parameterizes stratigraphic and topographic site effects by means of multiplicative coefficients. Expeditious methods are not available at present to account for basin effects in seismic design codes. Previous research suggests that two-dimensional aggravation factors may provide a convenient format to model two-dimensional basin effects starting from the simplified assignment of pseudo-spectral acceleration assigned from code-based approaches or one-dimensional site response analysis. Following on a previous study, this paper synthetically describes a work-in-progress approach to the quantitative calibration of two-dimensional aggravation factors for the seismic response analysis in basins. The approach relies on the development, implementation, and validation of a Python-based software suite which allows the generation of a large database of modelling schemes, the application of a set of seismic input motions, the conduction of 1D and 2D numerical analyses using the free OpenSeesPy package which leverages the modelling capabilities of OpenSees, and the subsequent statistical calibration of 2D aggravation factors. The general structure of the process is described, and initial example outputs are provided.