Typhoon Wind Field Observation, Construction and Structural Health Monitoring of a 600m High Skyscraper

颱風風場,超高層建築施工和結構健康監測研究

Student thesis: Doctoral Thesis

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Award date6 Jan 2021

Abstract

Numerous skyscrapers have been built in the past decades as a consequence of fast economic and social developments. Particularly, the new generation of skyscrapers is generally designed to be flexible and slender, which poses new challenges for their serviceability performance and safety under ambient excitations and extreme events. All these challenges further motivate the need to better understand the structural behaviors of those high-rise buildings through full-scale monitoring. In the context of such motivations, Ping-An Finance Center (PAFC) in Shenzhen, with a total height of about 600 m, is considered as a desirable full-scale test platform for the assessment of structural performance of skyscrapers. Consequently, structural static responses in relation to the vertical deformation of PAFC and its structural dynamic responses during the passage of typhoons, which are vital issues and widespread concerns about structural performances in the life cycle of skyscrapers from the beginning of construction to the whole service stage, are presented and discussed in this dissertation.

An integrated structural health monitoring (SHM) system with total number of 553 sensors, which was designed based on the modular design methodology, has been installed in PAFC to monitor its structural performance and external excitations during both construction and service stages. The modular design of the SHM system ensures highly effective operation of the comprehensive monitoring system, and such an extensible system allows the subsystems to be deployed and augmented easily to meet the evolving monitoring needs. Based on the outputs of the SHM system installed in PAFC, a combined study of both on-site measurements and numerical analysis of the vertical deformations (axial shortenings) of the skyscraper during its various construction stages is carried out. A novel strategy referred to as elevation reservation is implemented to adjust the elevation of each floor of PAFC in the design and construction of the building. Its effectiveness is verified through the field measurements of the vertical deformations in this study. A good agreement is found between the numerical results and the field measurements and the validated finite element models are further used to investigate the time-dependent effects due to the construction sequence and the shrinkage and creep of concrete on the vertical deformations. In the next part, this thesis presents the observations of wind fields in atmospheric boundary layer (ABL) and wind effects on the 600 m high skyscraper during typhoons. Specifically, wind structure and characteristics within the ABL are presented and discussed. Analysis of the observations, including wind speed, wind direction, pressures on building claddings and structural acceleration responses during typhoons, are carried out to investigate the typhoon-generated wind characteristics, structural vibrations and dynamic properties of the skyscraper under typhoon conditions. For the turbulence characteristics, it was found that the spectral analysis results demonstrated the reliability of the spectral estimation method for determining the turbulence integral length scale of winds based on the von Karman spectral model. For the vertical wind profiles, the well-fitted results indicated that the frequently used empirical models (log-law, power-law and D-H models) can provide reasonable predictions for the measured wind speed profiles. In addition, the boundary-layer vertical profiles of horizontal mean wind speed in the eyewall regions were characterized by a low-level jet (LLJ) and the effects of topography and terrain on the typhoon wind structure were evident. The observations of cladding pressures revealed that the maximum peak negative pressures likely occurred at building corners or concave regions. Probability distributions of negative pressures illustrated distinct non-Gaussian characteristics while those of positive pressures appeared to follow the normal distribution. Moreover, the mean pressure coefficients obtained from the field measurements during typhoons at the building central locations were in good agreement with those stipulated in the load code of China (GB50009-2012). On the basis of the field measurements, the range of selection of damping ratio for the wind-resistant design of super-tall buildings is recommended and the serviceability of the skyscraper under typhoon conditions is assessed. The outcomes of this dissertation would be of interest and practical use for engineers and researchers involved in the structural design, construction, and structural health monitoring of super tall buildings.