## 5 Conclusions  
Taking Renwan Ruhe Special Bridge as the engineering focus, the following aspects were investigated: the characteristics of the long-period ground shaking and its components based on two component separation methods; the correlation of the displacement response of the structure under the action of long-period ground shaking and its components; the response characteristics of the ground shaking components for different periods of the structure based on the MEEMD; and the analysis of the characteristics of the internal force response under the action of ordinary and long-period ground shaking. The conclusions can be summarized as follows:  
1. By Comparing the two long-period component decomposition methods, EMD and MEEMD, it was found that the component acceleration time-range curves after the reconstruction of the two methods were similar; however, there was a large difference between the velocity time-range curves and the displacement time-range curves. The validity of the two component separation methods was verified by the response correlation acting on the bridge, and the comparison revealed that the MEEMD better separated the low-frequency components and more accurately reflected the long-period characteristics of the ground shaking. The MEEMD is a good choice for demonstrating the low-frequency components of long-period ground shaking. 2. From the seismic responses of the two different natural period structures, it was observed that the short-period structures were more sensitive to the short-period component of the ground shaking and were prone to resonance-like effects, while they were less sensitive to the long-period component. Similarly, the long-period structures were more sensitive to the long-period component of ground shaking, while they had a similar \"filtering\" effect on the short-period seismic component, which made the seismic response of long-period structures more obvious. The seismic response of the structure had a high correlation with the self-oscillation period and seismic spectral characteristics of the structure; hence, the seismic analysis of long-period bridge structures should pay special attention to the action of long-period earthquakes. 3. Compared with ordinary ground shaking, the response of the structure to long-period ground shaking had a more obvious amplification effect; in the two kinds of long-period ground shaking, the structural displacement caused by the far-field long-period ground shaking had a higher internal force response than that caused by the near-field long-period ground shaking. In this paper, it is verified that the effectiveness of the long period component extraction method based on the MEEMD method is better than the EMD method, and the long period component extracted by MEEMD can reflect the original long period ground vibration to a certain extent, which provides a direction and basis for us to further study the long period ground vibration, and we can define the long period ground vibration by investigating the spectral characteristics, time-holding characteristics, peak characteristics, and energy characteristics of long period component; however, this paper only reflects the amplification effect of the long period component from the high pier large span structure, which has limitations in the selection of structural forms; the paper only considers the average period of the ground vibration component response spectrum. However, this article only reflects the amplification effect of the long-period component from the high pier and large span structure, which has limitations in the selection of structural form; the average period of the response spectrum of the ground vibration component, Tr, is only considered as a spectral parameter indicator in the paper, which shows that the self-oscillation period of the structure is correlated with the spectral characteristics of the ground vibration, and the parameter indicators have some limitations in the selection of the parameter indicators.