Bi-directional Ground Motion Records Selection Methods For Structural Seismic Fragility Analysis

Structural seismic vulnerability analysis is an important research content based on aseismic design and seismic performance evaluation,and the first problem to be solved in seismic vulnerability analysis is how to select ground motion records.The results of the investigation of earthquake damage and the study of seismic theory all show that the seismic action is multi-dimensional and the actual engineering structure is also a three-dimensional space.Therefore,it is not comprehensive and unreasonable to consider the effect of seismic action under unidirectional input on structural seismic vulnerability only,and it will underestimate the structure.The seismic response under the action of an earthquake.With the development of the seismic theory,the improvement of the numerical calculation capacity of the structure and the improvement of the structural safety requirements of the actual engineering,the engineering community has gradually begun to pay attention to the structural seismic response analysis of the structure in the action of the two-way(three-way)earthquake.However,there are still some problems to be solved in the two-way seismic input to the structure.For example,how to select the ground motion parameters,how to select two-way seismic records.Based on this,this paper studies the selection of ground motion intensity parameters,the selection method of two-way input ground motion and the difference of structural seismic vulnerability analysis under single and bi-directional input.The main research contents are as follows:(1)Based on the finite element software OpenSEES,a typical three-dimensional frame structure model for structural seismic vulnerability analysis was established.The validity of the built finite element model was validated from the three dimensions of the overall dynamic characteristics of the structure,the structural components and the overall structural hysteretic performance,which laid the foundation for subsequent research and analysis.(2)In the selection of ground motion records,firstly,the characteristics of 24 ground motion intensity parameters were summarized and summarized.Then,the distance analysis and Pearson correlation analysis method were used to evaluate the practicality and combinability of ground motion intensity parameters.Finally,through nonlinear time-history analysis,statistical regression analysis of the maximum seismic response(maximum inter-story displacement angle)of the seismic intensity parameters and the earthquake-induced structure is performed from several aspects of correlation,validity,practicality,and efficiency.Evaluate and optimize the required ground motion intensity parameters for the selection of bi-directional ground motion records.(3)The selection of two-way input ground motion records(groups)for structural seismic vulnerability analysis takes into account that the single ground motion intensity parameters do not fully reflect the impact of ground motion characteristics on structural seismic vulnerability.The combination of the characteristic magnitude M and the epicentral distance R,and the combination of peak ground acceleration PGA and excellent period Tp in consideration of the ground motion peak characteristics and site conditions,are used to screen bidirectional ground motion records,and it is recommended that the relevant parameters used in selecting ground motion records be reasonable.Ranges.Finally,through the comparative analysis of structural seismic vulnerability analysis results under single and bidirectional input,the necessity of the two-way seismic vulnerability analysis of the structure is illustrated,and the validity of the bidirectional ground motion record selection method is verified.