| Time history analysis method has become the core method in the seismic design codes of most countries, and with large number of strong earthquake records obtained, how to choose reasonable seismic records becomes a hotspot research in recent years. Based on the different methods proposed by the domestic and foreign scholars to select seismic records, a comprehensive review was made in this paper. In addition, the method introducing the normalized modal participation factor was mainly focused on considering the influence of higher modes on the structure. For the benchmark steel moment resisting frame structures, the average response of the maximum inter-story drift angle has been calculated when subjected to 20 far-fault ground motions and 20 near-fault ground motions, respectively, aiming to verify the applicability of the proposed method in the structural nonlinear time history analysis and compare with the earthquake records selection and adjustment method in the United States ASCE7-05 code. The main contents are as follows:(1) The requirement of the input earthquake records for time history analysis has been reviewed based on the domestic and foreign seismic design codes and the earthquake records selection methods proposed by different scholars has been summarized. This paper also introduced the method which considered the influence of higher modes on the structure and the earthquake records selection and adjustment method in United States ASCE7-05 code.(2) Taking the 3-,9- and 20- Story Benchmark steel moment resisting frame structures proposed by the United States SAC Steel Project as examples, the numerical models have been built using SAP2000 software. The feasibility of the numerical models was verified by the analysis of structural natural vibration characteristic and the comparisons between the time history analysis results of different nonlinear beam-column elements models (elements with lumped plastic hinges and elements with distributed plastic hinges, respectively).(3) Twenty far-fault ground motions were selected as the sample, which were recorded by 10 stations in two horizontal directions in different earthquakes. According to the method proposed in this paper to reasonably choose the seismic records,3 earthquake records were chosen from the sample. Besides, another 7 earthquake records were chosen based on the requirement of ASCE7-05 code. All the two groups of earthquake records were used to carry out the dynamic analyses for the 3-,9- and 20- Story Benchmark steel moment resisting frame structures, and the corresponding maximum inter-story drift angles could be obtained. It was verified that the proposed method was applicable for the lower structure (3-Story), while for the medium and high-level structures (9-Story and 20-Story), the maximum inter-story drift angle of structures were sometimes undervalued, and the calculation results had an error from 15% to 30%. But according to the judgment of the weakest and the second weakest floor and the calculation of the inter-story drift angle, the average value obtained from the proposed method was consistent with that calculated from the 20 earthquake records. As for the ASCE7-05 method, the calculated maximum inter-story drift angle of the structure and its distribution along the floor were close to the average value obtained from the 20 earthquake records for different PGAs, and the calculated values of the ASCE7-05 method were about 20% larger. However, the maximum inter-story drift angle was not underestimated by the ASCE7-05 method. The recognition of the weakest floor and the second weakest floor numbers were consistent for both the proposed method and the ASCE7-05 method, but the calculated maximum inter-story drift angle by the proposed method in this paper was larger.(4) Twenty near-fault ground motions containing the velocity pulses were selected as another sample, which were recorded by 20 stations in different earthquakes. Taking the 9-and 20- Story Benchmark steel moment resisting frame structures as examples, this paper analyzed the applicability of the proposed method and ASCE7-05 method when subjected to near-fault earthquake records. For the 9- Story Benchmark steel moment resisting frame structure under the near-fault seismic loads, the maximum inter-story drift angle and its distribution along the floor calculated by the proposed method in this paper were closer to the average value when subjected to the 20 near-fault earthquake records. But for the 20-Story Benchmark steel moment resisting frame structure, the maximum inter-story drift angle calculated by the proposed method appeared simultaneously in the 3rd,4th and 11th floor, the corresponding values were 1/37,1/38 and 1/38, respectively, and the relative error was less than 3.9%. But the maximum inter-story drift angle calculated by 20 earthquake records and ASCE7-05 method appeared in the 3rd floor, and the corresponding values of the maximum inter-story drift angle were 1/42 and 1/27, respectively, which meant that the proposed method was consistent with the ASCE7-05 method.It could be concluded that the method proposed in this paper is applicable for nonlinear seismic analysis of practical structure, either far-fault or near-fault earthquake records input. Considering the suggestion of the ASCE7-05 regulations, when the proposed method is adopted in the practical engineering, it is recommended to meet the additional condition that "within the range of 0.2T and 1.5T, the average spectrum of the 3 seismic records should be displayed above the target spectrum or design spectrum", so that the underestimation of the structural seismic response could be prevented. |
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