传递函数在地下工程地震响应研究中的应用

将传递函数引入地下工程地震响应的研究，提出利用传递函数进行地下工程地震响应的频谱特性分析、地震响应时频估算以及地震动输入频谱修正的3种应用方法。基于白鹤滩水电站13#机组剖面地下洞室群，对这3种方法进行了探讨及检验。结果表明：传递函数可清晰表达地下工程在地震动作用下的输入、输出关系，描述洞室群各部位的动力特性，且与其他频谱特性研究方法得出的结论相一致。在自下而上的地震剪切波作用下，洞室底板部位的响应整体强于顶拱部位，且具有不同的主频段；但在3～4 Hz频段，顶拱的动力响应强于底板。采用有限带宽随机白噪声算得洞室群各部位的传递函数，再根据传递函数进行实际地震响应时频估算的方法是可行的，估算与验算结果吻合良好，该方法可以大幅度减少计算量，使得根据有限的计算结果把握特定工程的整体动力响应特征成为可能。根据已有研究成果，取洞室底部或河谷水面为地震响应的频谱控制点，基于传递函数对输入地震动时程进行频谱修正，可保证地下工程动力响应地震动输入机制的合理性

Application study of transfer function for seismic response analysis of underground engineering

Based on transfer function,the three procedures of spectral characteristics analysis,seismic response time-frequency estimation,and the spectral correction for input ground motion are proposed.Discussion and verification for these procedures are made based on the seismic analysis of Baihetan hydropower station underground power houses.The results indicate that the seismic input-output relation for underground engineering can be clearly expressed by transfer function.The results are well consistent with the conclusion made by the other methods.Generally the response of floor may be stronger than that of crown,and may contain different main frequency bands.However the response of floor is smaller than that of crown in the band of 3-4 Hz.The method of seismic response time-frequency estimation made with transfer function and based on white noise calculation is feasible.It is believed that this procedure can greatly reduce the time-consuming computation,and makes it possible to grasp the main seismic response characteristics of target project with limited amount of computation.Moreover,the correction of spectral characteristics for the input ground motion to correspond with the spectral reference points of carven bottom or the water level of valley can guarantee the reasonable mechanism of the input ground motion.