Investigation of Tropical Cyclone Effects on Super-tall Buildings Based on Field Measurements and Wind Tunnel Tests

Abstract

From the viewpoint of structural engineering, wind effects are of great concern in the design of high-rise buildings, especially those located in regions prone to tropical cyclones (TCs). This dissertation presents a comprehensive study of the wind effects on super-tall buildings (over 300 m in height) by means of full-scale field measurements during TC events and experiments conducted in a boundary layer wind tunnel.

First, this research analyzes the wind characteristics of 16 violent TCs affected Hong Kong from 2008 to 2018. By employing the field measurements obtained by anemometers and Doppler radar profiler systems at locations corresponding to different terrain categories (e.g., open sea, mountainous, urban terrains), structures of these monitored TCs are revealed and features such as low-level jet are observed. Moreover, based on the records collected by the anemometers mounted atop a 420-m-high super-tall building with a total time duration of 399 hours, the wind characteristics of TCs over a densely built-up urban terrain are analyzed in detail and described statistically.

Subsequently, using field measurements collected by a long-term structural health monitoring system, this thesis investigates the structural performance of the aforementioned super-tall building during 15 TCs from 2008 to 2017. The correlations between the wind-induced structural dynamic responses (i.e., accelerations and displacements) and the approaching wind characteristics are presented, the resonant and quasi-static background components of the structural responses are investigated, and the building serviceability (or habitability) under severe wind effects is evaluated against multiple comfort criteria. Furthermore, the structural dynamic properties of the super-tall building such as natural frequency and damping ratio are estimated using modal identification methods such as the random decrement technique (RDT), which is a deterministic time-domain method, and the Bayesian spectral density approach (BSDA), which is a recently developed probabilistic frequency-domain method. Due to the usage of a substantial amount of field measurement data, this study not only significantly improves the accuracy and reliability of the RDT estimates but also proposes a method that allows the amplitude-dependencies of modal parameters to be estimated by the BSDA.

Next, the present study validates the existing wind tunnel testing techniques, namely, the high-frequency force balance technique, the synchronous multi-pressure sensing system, and the aeroelastic modelling. Both rigid (i.e., force and pressure test) and aeroelastic test models of the monitored super-tall building were fabricated, and particularly the aeroelastic model was precisely calibrated following the modal parameters measured directly from the prototype building. Using the field measurements of the monitored building collected during TCs, the wind tunnel predictions of structural acceleration and displacement responses are validated.

A case study is then presented to discuss the wind effects on two super-tall buildings in Hong Kong during Typhoon Mangkhut (1822) in September 2018, which is a remarkably violent typhoon corresponding to a return period of almost 50 years, based on 24-hour-long field measurement data collected in the buildings as well as at nearby meteorological stations. Structural performances of the two monitored buildings under extremely high wind speeds are evaluated, and the wind tunnel predictions of structural responses under such fierce winds are validated.

In addition, a study adopting field measurement data obtained from 9 super-tall buildings located in Hong Kong, Taiwan, and mainland China during TCs is conducted. With heights from 384 to 600 m, these monitored buildings are currently among the list of the 30 tallest buildings in the world and therefore the investigation on their modal parameters and structural performance during TCs are of great importance for the designs of future high-rise buildings. Based on the field measurements, this study proposes an empirical model for natural frequency and suggests a damping ratio for the design of super-tall buildings.

This thesis also presents an experimental study of the interference effects between twin tapered skyscrapers using wind tunnel testing. The interference effects on the structural overall turning moments and the wind pressures on building facades are investigated, and the contribution by the interfering distance and by the interfering angle are identified separately with the employment of a polar coordinate system.

In this dissertation, the wind characteristics of landfall TCs over Hong Kong are investigated in detail, the structural performance of super-tall buildings excited by TC winds are evaluated, the structural dynamic properties of super-tall buildings are estimated, and various wind tunnel testing techniques using rigid and aeroelastic models are validated by the field measurements. The primary objective of this research is to further the understanding of the wind effects on high-rise buildings, especially those located in TC-prone regions.

Date of Award	27 Mar 2019
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Qiusheng LI (Supervisor)