A new method to assess spatial variations of outdoor thermal comfort: Onsite monitoring results and implications for precinct planning

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Effects of coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness on wind-excited tall buildings

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BRA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model

Interference excitation mechanisms on a 3DOF aeroelastic CAARC building model

A comprehensive wind tunnel test program was conducted to investigate interference excitation mechanisms on translational and torsional responses of an identical pair of tall buildings. Motion responses of a three-degree-of-freedom aeroelastic building model were measured. Both upstream and downstream interference effects were studied in this research. The experimental results showed that with an open terrain wind model, both dynamic translational and dynamic torsional responses generally increased under interference effects for an operating reduced wind velocity of 6. Measured response spectra indicated that amplified along-wind, cross-wind and torsional responses were largely induced by the wake of an upstream interfering building. The significance of interference effects and the dominant interference mechanisms depended upon the location of the aeroelastic model in the wake region. Furthermore, coupled translational-torsional motion of the aeroelastic building model tested was found to cause only small increases in the resultant motions at the building corner. (C) 2004 Elsevier Ltd. All rights reserved

Wind-induced responses of tall buildings experiencing complex motion

A wind tunnel model study on the effects of eccentricity between centre of mass and centre of stiffness of a tall rectangular building on the wind-induced response characteristics and wind excitation mechanisms was carried out. The results indicated significant effects of eccentricity on the along-wind, cross-wind, and twisting moment responses for both cases of the incident wind normal to the narrow and wide faces of the building model. The periodic twisting moments, created either by the flow separation at the upstream corners and the reattachment process of the separated shear layers, or by the eccentricity between the resultant lift force and centre of stiffness, were found to be a dominant wind excitation mechanism causing a significant increase in the twisting moment response of the building model. In addition, the twisting moment responses could be greatly amplified by the effects of resonance between the frequency of the periodic twisting moment and the torsional natural frequency of the building model. For the building model with the centre of stiffness located downstream from the centre of mass, increases in the twisting moment response and the resultant acceleration response at the corner of the building model were more prominent. (C) 2002 Elsevier Science Ltd. All rights reserved

Vibration control of wind-excited buildings and structures

Full-scale measurements of the dynamic characteristics and wind-induced responses of a variety of buildings and structures are presented. The usefulness of these measurements, in terms of the prediction, and actual behaviour, of buildings and structures under wind action, and the design and effectiveness assessment of vibration control devices are discussed

Dynamic measurements on tall buildings and structures

Techniques and instrumentation currently employed to measure the dynamic properties of tall buildings and structures and their responses in strong winds are presented. The merits and limitations of these techniques are discussed. Natural frequencies of vibration, deflected mode shapes and damping values can be determined reliably through dynamic measurements on actual buildings and these results provide invaluable validations of numerical modelling techniques and generalised prediction formulae. The improved accuracy of prediction processes, coupled with a better understanding of building performance in strong minds, through long-term building monitoring, can lead to significant cost savings in the wind-resistant design and construction of tall buildings

Dynamic characteristics and wind-induced response of two high-rise residential buildings during typhoons

Two high-rise residential buildings in Hong Kong, among the tallest ill the world, were equipped to monitor their wind-induced dynamic response. The effects of typhoon Imbudo and typhoon Dujan on the buildings are presented in detail. Upcrossing analyses performed oil the acceleration data indicate the wind-induced response of the buildings during typhoons Imbudo and Dujuan follow a Gaussian distribution. Natural frequencies of vibration in two orthogonal translational and torsional directions are estimated by empirical, numerical, and experimental techniques. A comparison between these natural frequencies reveals that experimental values are higher than empirically or numerically predicted values. This finding suggests that tall, reinforced concrete (RC) buildings in Hong Kong are stiffer than similar buildings in other Countries. (c) 2005 Published by Elsevier Ltd

Interference effects on wind-induced coupled motion of a tall building

Interference effects from neighbouring buildings on wind-induced coupled translational-torsional motion of tall buildings have been investigated through a series of wind tunnel aeroelastic model tests. Interference effects on the CAARC standard tall building by an 8: 1:1 tall interfering building both upstream and downstream were investigated. The results indicated a significant increase in responses at the critical wind speed where the frequency of the shed vortices originated from the interfering building coincides with the modal natural frequency of vibration of the principal tall building. The along-wind, cross-wind, and twisting moment responses of the principal building were significantly increased when the interfering building was located diagonally upstream. A more substantial increase in responses was evident when the interfering building was located directly upstream from the principal building. (C) 2002 Elsevier Science Ltd. All rights reserved