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This paper investigates the impact of Super Typhoon Mangkhut on Hong Kong, especially the wind effects on high-rise buildings, based on 24-h-long field measurement records collected from the two tallest skyscrapers (484 and 420 m in height) in the metropolis and six meteorological stations on different types of terrain on September 16, 2018. Mangkhut corresponded to a 50-year return period and was the most violent typhoon since wind records in Hong Kong began in 1946. In this large-scale monitoring study, the wind characteristics of Mangkhut over different terrains are investigated using the climate records by anemometers and a weather surveillance radar, the wind-excited structural responses of the monitored skyscrapers are analyzed according to measurements by accelerometers and a global navigation satellite system, the structural dynamic properties are estimated by the random decrement technique and the Bayesian spectral density approach, and both rigid and aeroelastic modeling techniques for wind tunnel testing are validated by in-situ measurements during the typhoon. This study aims to enhance the understanding of strong typhoon-generated wind characteristics over different terrains and provide comprehensive information for the wind-resistant design of high-rise buildings in tropical cyclone-prone regions. [ABSTRACT FROM AUTHOR]

Typhoon winds near the external eye wall of a strong typhoon are extremely nonstationary and disastrous due to its vortex and convective origin as well as its high wind speeds. However, typhoon-induced nonstationary responses of long-span bridges are currently analyzed with the assumption of time-invariant wind coherence. By taking the Stonecutters cable-stayed bridge in Hong Kong under Typhoon Hato in 2017 as an example, this paper presents the time-varying wind spectra and coherences for the bridge based on the wind data recorded by the multiple anemometers installed on the bridge. The analytical framework for nonstationary buffeting analysis of long-span bridges under typhoon winds is enhanced by considering time-varying wind coherence and applied to the Stonecutters Bridge under Typhoon Hato. The computed responses are compared with the field measurement responses. The comparative results demonstrate the feasibility and accuracy of the enhanced framework for buffeting analysis of long-span bridges with time-varying wind spectra and coherences. Comparative results with the other two cases of time-invariant coherence functions also highlight the importance and necessity of considering the time-varying wind coherence in the nonstationary buffeting analysis of long-span bridges under typhoon winds. [ABSTRACT FROM AUTHOR]

A wind and structural health monitoring system (WASHMS) was installed in the Tsing Ma suspension bridge in Hong Kong in 1997. On September 16, 1999, Typhoon York, which was the strongest typhoon since 1983 and the typhoon of the longest duration on record, crossed over Hong Kong. All vehicles, except trains, were prohibited from running on the bridge for 2.5 h. This event provided a distinctive opportunity to examine the existing analytical models for predicting dynamic response of long suspension bridges to high winds and running trains. The field measurement data recorded by the WASHMS during this event were therefore analyzed and the four particular cases were identified and discussed in this paper. The four particular cases identified included: (1) the bridge without any vehicles; (2) the bridge with one train; (3) the bridge with two trains running in opposite directions; and (4) the bridge with three running trains. The mean wind speed was almost perpendicular to the bridge alignment in the four cases to facilitate the comparison with analytical results. For each case, wind characteristics, bridge acceleration responses, and bridge displacement responses were analyzed using the measurement data from anemometers, accelerometers, and level sensing systems, respectively. The number of trains running on the bridge, train speed, and train location were also identified using the measurement data from strain gauges. The measurement results clearly demonstrated the dynamic behavior of the bridge with running trains during high winds. The measurement results obtained will also be used to verify the analytical model developed by the authors in the companion paper. [ABSTRACT FROM AUTHOR]

The field measurement results of the Tsing Ma suspension bridge under cross winds and running trains during Typhoon York have been presented in Part I of this study. The field measurement results are used in this paper (Paper II) to verify, to some extent, the finite element based framework developed by the writers in the time domain for predicting dynamic response of coupled train and bridge systems in cross winds. In this regard, a three-dimensional finite element model is used to model the Tsing Ma suspension bridge. Wind forces acting on the bridge are generated in the time domain using a fast spectral representation method and based on the field measurement results and wind tunnel test results. Each coach in a train running on the bridge is modeled by a 27 degree-of-freedom dynamic system. The dynamic interaction between the bridge and the train is realized through the contact forces between the wheels and the track. Track irregularity is simulated using a high-order multivariate autoregressive model, whereas wheel hunting is assumed to be a sinusoidal function with a random phase. The acceleration and displacement responses of the bridge under cross winds and running trains are computed and compared with the responses measured from the field for four cases. The comparison is found to be satisfactory in general. The dynamic response and performance of trains on the bridge is also computed and evaluated. The proposed framework is found to be feasible and practical. [ABSTRACT FROM AUTHOR]

This paper presents work on validating the dynamic wind load predicted by a wind tunnel model with the values identified from full-scale field vibration data of a super-tall building in Hong Kong. Dynamic wind load in this work refers to the power spectral density (PSD) of the modal force near the natural frequency of a particular mode of the building, in the context of random vibration with stationary loading and response. This quantity reflects the turbulence characteristics integrated over the building body and is of importance in wind engineering design. This study presents a method to predict the modal PSD of wind load of the first two translational modes of a tall building. The method combines wind tunnel test information and mean wind data available in the free field; the latter taken to be at the Waglan Island station maintained by the Hong Kong Observatory. On the full-scale side, although the modal PSD is not directly observable, it is identified from field vibration data measured at the building top during strong wind events. A Bayesian modal identification method is used for determining the most probable value and the uncertainty of the modal parameters including the natural frequency, damping ratio, and the modal PSD. A number of recent strong wind events are analyzed. Reasonable agreement is observed between the wind tunnel model predictions and the values identified from field data. Factors that can potentially lead to discrepancy are discussed. As the same random vibration modeling consistent with conventional wind engineering design has been used in the wind tunnel prediction model and field identification model, the results are directly transferable among these three disciplines. [ABSTRACT FROM AUTHOR]