This thesis presents the results of a study of interference effects and excitation mechanisms on wind-excited centric and eccentric tall buildings through wind tunnel test on a Commonwealth Advisory Aeronautical Research Council (CAARC) standard building model by using base balance and pressure measurement techniques. Some of the excitation mechanism that were thought to be motion dependent were investigated by comparing the result obtained by using base balance technique and aeroelastic modelling technique. Interference effects were provided by an identical rigid building model located at different positions upstream of downstream of the principal building....[ Read more ]

This thesis presents the results of a study of interference effects and excitation mechanisms on wind-excited centric and eccentric tall buildings through wind tunnel test on a Commonwealth Advisory Aeronautical Research Council (CAARC) standard building model by using base balance and pressure measurement techniques. Some of the excitation mechanism that were thought to be motion dependent were investigated by comparing the result obtained by using base balance technique and aeroelastic modelling technique. Interference effects were provided by an identical rigid building model located at different positions upstream of downstream of the principal building.

Wind tunnel tests were conducted in an open terrain wind model. A torsional/translational frequency ratio of 1.5 was adopted for rigid model testing techniques. At the reduced wind velocity of 6, the centric building responses could be enhanced by as high as 80%. However, the enhancement was not always the result of interference for all building arrangements. The building responses could be decreased by almost 50% in some cases depending on the interfering building location.

Under the same approaching flow condition, the normalized torque spectra of the isolated CAARC Building model, with different locations for the center of mass and center of stiffness can be altered significantly. Information gathered from pressure measurements indicated that the differences in the spectral characteristics of the normalized torque spectra are due to the pressure distribution around the building model and the correlations between certain frequency components of the torque of particular part of the building.

Interference effects on the centric and eccentric CAARC Building model were studied by using base balance techniques. The results show that, for a particular building arrangement, relocating the center of mass and center of stiffness of the building changed the standard deviation twist angle responses. The changes depended on the combination of building arrangement and location of center of mass and center of stiffness.

The study also found that the combined effects of the flow and the wind-induced loads on the building, determined by base balance tests, may mask the dominant excitation mechanism on the building. By using wind pressure measurement technique, a better understanding of the flow characteristics and the corresponding wind-induced loads for tall building under interference can be achieved, facilitating a better structural design of tall building.

Interference effects on the CAARC Building model were studied by using base balance technique and aeroelastic modelling technique. Comparison of the buffeting factor contours of the building responses obtained by both modelling technique found that the magnitude of the buffeting factors and the pattern of the buffeting factor contour of building responses obtained by both modelling technique are very close to each others. The critical locations identified from the buffeting factor contours of building responses occurred in proximate locations. The percentage difference between the buffeting factors of the building responses at the critical locations are usually within 16 %.

Moreover, the dependency on motion of the downstream interference excitation mechanism is investigated by comparing the excitation spectra obtained by using base balance technique and aeroelastic modelling technique. It has been concluded that the energy distribution and the magnitude of the spectral density of the force spectrum is independent of the modelling techniques that were adopted. This means that the downstream interference excitation mechanism is not dependent on the motion of the building.