# Structural Responses of a Superall Building Subjected to a Severe Typhoon at Landfall
## 5 Conclusions  
In this study, field measurements collected at multiple height levels of a 303 m high building during the passage of a severe typhoon were analyzed to explore the dynamic properties of and the associated wind effects on the building. The relationship between the structural response and the wind strength was examined. Comfort assessment was conducted by comparing the maximum acceleration response with recommendations from several reference sources. Emphasis was paid to the identification of modal parameters via different methods and their dependence upon wind strength or the amplitude of structural vibration. Main conclusions and discussions are summarized as follows. 1. Although Typhoon Mangkhut was one of the strongest tropical cyclones to have ever impacted the study region, and the maximum peak gust wind speed was recorded as 56.5 m/s at the study site, the maximum structural response at the top floor (260 m) of Leatop Plaza was only 8.98 cm/s\({}^{2}\), which is well below the critical levels for conform assessment as recommended in several reference sources. Practically, one may use the peak factor method to predict the peak structural response based on SD values of building responses that can be easily estimated through wind tunnel testing techniques, given the values of peak factor and other modal information. In this study, the measured peak factors for the fundamental modal response were found in a range of 2.97-3.25, which are a bit lower than the theoretical values. The reason is mainly attributed to the fact that response signals deviate from a Gaussian distribution pattern. Thus, more advanced techniques may be adopted to better predict the values of peak factor. Measurement results also show that the SD values of building response increased exponentially with mean wind speed, with the power exponent equal to 2.05-2.40. This indicates that high-rise buildings are considerably sensitive to wind load. 2. Results of modal parameters identified via the SSI method and other alternative methods (including the RDT method and the RMS method) basically show good agreement, which indicates the validity and the accuracy of the adopted methods. However, it must be noted that the SSI method is much more efficient, since it can provide results of natural frequency, damping ratio, and mode shape for multiple modes simultaneously, while the alternative methods can be only employed to deal with SDOF problems. More importantly, the alternative methods should be used in conjunction with filtering techniques whose working performance may differ significantly with users depending upon their experience. Thus, the SSI method is regarded as a preferred method for modal analysis. 3. Both natural frequency and damping ratio demonstrated noticeable amplitude-dependence features. While the natural frequencies decreased slightly with increasing structural response, the damping ratios increased markedly as the structure response became stronger. For the first swaying mode, the measured damping ratios varied in a range of 0.4-1.2%, which is a bit smaller than the recommendations in many codes and standards. The above findings provide useful insights to explore the nonlinear dynamic properties of building structures. 4. The performance of five empirical predictors for natural frequency was examined, and the one proposed by [PERSON] et al. [43] was found to provide the best predictions for the study building. The performance of two empirical predictors for first swaying mode shape and first torsional mode shape were examined as well, results from both of which agreed well with those obtained from measurements. It is also observed that the first swaying mode shape did not follow a linear