# Inter-Story Drift Ratio Detection of High-Rise Buildings Based on Ambient Noise Recordings
## 5 Conclusions  
In this paper, a monitoring approach was proposed based on ambient noise recordings to measure IDRs of structures and monitor the structural health through three parameters: the total IDR, the maximum IDR, and harmful IDRs. The feasibility of the proposed method was investigated through a field test using the Zhonghe Building on the campus of Tongji University, Shanghai, China. The results indicate:  
1. The IDRs of the Zhonghe Building can be monitored using ambient noise. 2. The parameter \(\tan\Delta\theta_{1}\) of the building's structure can be approximately regarded as the tangent slope of the deflection curve at one point. Figure 9: Diagram of harmful IDRs and IDR limit. 3. The data set for \(\Delta\theta_{1}\) and the height can be used to fit the deflection function of the building. 4. Using the deflection function, IDRs can be calculated. 5. The calculation of harmful IDRs can be integrated using IDR data and the secant method. The dangerous places indicated by harmful IDRs and IDRs are different. Structures on the 6 th floor and 19 th floor may need more attention when storms occur. 6. The credible IDRs of the Zhonghe Building of Tongji University during the measurement period were far lower than the IDR limit required by the Chinese standards. The overall structure is reliable. The use of ambient noise recordings provides a very attractive alternative for current optical IDR monitoring measurement applications. Ambient noise recordings were able to provide detailed and continuous information on the IDRs of structures and partially solved some problems in application, e.g., adverse effects from weather, requirement for large amounts of space, and fragile instruments, in comparison to the conventional method using total stations. The proposed monitoring approach was proven to be credible in the measurement of IDRs. This study demonstrated the applicability and potential of the monitoring system based on ambient noise recordings for the monitoring of structural health. Assumptions on the distribution of structural stress and wind loads were accepted for generality since they can effectively generalize the typical conditions of most buildings in great gates. Therefore, the proposed approach was first tested based on these assumptions. It should be noted that actual buildings and wind loads may be much more complex, with different boundary conditions, e.g., body type of buildings, distribution of wind loads, topographic conditions, etc. In future work, the proposed method should be tested on such complex conditions and be strictly compared with the work of total stations. Additionally, apart from the assumptions and limitations stated throughout the article, adequate consideration should be given to the inevitable uncertainties. Future research will focus on establishing an intelligent monitoring system for IDRs with functions of localized computing, real-time information updating, and network transmission. In this system, seismometers fixed indoors will record raw data and transmit them online; meanwhile, a data center records transient \(\theta_{1}\) and the median of the collected \(\theta_{1}\) in real time and provides real-time IDRs and a dynamic result on structural health. Ambient noises are continuous seismic waves, meaning that their greatest potential is the ability to provide continuous and real-time information of building structures. In the future, structural health monitoring may focus more on real-time changes in structure, and at that time, the proposed method providing real-time information on IDRs of structures will play an important role. Future studies will also include practical applications in the laboratory and on existing buildings. Additionally, future studies should include applications in the resilience monitoring and structural design optimization of buildings during earthquakes.