弹性时程分析法中地震动的双参数调选方法

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

关键词:  时程分析法  近场地震  调选方法  因果推断  XGBoost算法

Key words:  time-history analysis method  near-fault earthquake  modulation and selection method  causal inference  extreme gradient boosting algorithm

摘要:

针对现行规范采用弹性时程分析法验算时存在的基底剪力结果离散性过大和对近场地震特性考虑不足的问题,提出基于双参数的地震动记录调选方法。首先,采用规范中的调幅参数对地震动记录进行第1次调选；其次,采用因果推断筛选出对结构基底剪力影响最大的地震动参数,作为筛选参数；最后,指定筛选参数的取值范围,对第1次调选出的地震动记录进行再次筛选。作为已有调选方法的补充,以四川省泸定县磨西台地某博物馆为例,采用300条天然地震动记录,对弹性时程分析中地震动记录的规范调幅方法、双参数调选方法进行对比分析。结果表明:对于断层距小于等于60 km的地震动记录,加速度相关的地震动参数对结构基底剪力的影响较大,其中,Park-Ang指标的影响最大；双参数法在保证结构安全裕度不低于规范要求的前提下,可以有效地控制基底剪力的离散性,相比规范法,经过双参数法调选时程分析得到的基底剪力标准差的降幅可达到25%以上；由于基底剪力的离散性可以被很好地控制,当采用双参数法时,对于近场地震多发区特别不规则的建筑,弹性时程补充验算中可不必采用人工地震动记录。

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.