Dual parameter modulation and selection method of ground motions in elastic time history analysis

Abstract:

In response to the issues of significant dispersion in base shear results and inadequate consideration of near-field seismic characteristics when using the elastic time-history analysis method for checking calculations in current codes, a method for selecting seismic records based on dual parameters is proposed. Initially, the method employs the amplitude modulation parameters specified in the code to perform the first selection of seismic records. Subsequently, causal inference is utilized to identify the seismic ground motion parameters that have the most significant impact on structural base shear, serving as the screening parameters. Lastly, by specifying the value range for the screening parameters, a re-screening is conducted on the seismic records selected in the first stage. As a complement to existing seismic selection methods, a comparative analysis is conducted on the standard amplitude modulation method and the dual-parameter selection method for seismic records in elastic time-history analysis, using 300 natural earthquake records from a museum located on the Moxi Plateau in Luding County, Sichuan Province as a case study. The research results indicate that for seismic records with a fault distance less than or equal to 60 km, acceleration related seismic parameters have a significant impact on the base shear force of the structure, with the Park-Ang index having the greatest influence. The dual parameter method can effectively control the discreteness of the base shear force while ensuring that the structural safety margin meets or exceeds specification requirements. Compared with the specification method, the reduction in the standard deviation of the base shear force obtained through time history analysis using the dual parameter method can reach more than 25%. Due to the good control of the discreteness of the base shear force, when using the dual parameter method, for particularly irregular buildings in near-fault earthquake prone areas, artificial seismic motion records may not be necessasry in the elastic time history supplementary calculation.