Interference effects of wind-excited tall buildings
by Tang Un Fong
M.Phil. Civil Engineering
xxiv, 142 leaves : ill. ; 30 cm
This thesis presents the results of a study of interference effects and excitation mechanisms on wind-excited tall buildings through wind tunnel model tests on a Commonwealth Advisory Aeronautical Research Council (CAARC) standard building model using a newly-developed three-degree-of-freedom aeroelastic test rig ....[ Read more ]
This thesis presents the results of a study of interference effects and excitation mechanisms on wind-excited tall buildings through wind tunnel model tests on a Commonwealth Advisory Aeronautical Research Council (CAARC) standard building model using a newly-developed three-degree-of-freedom aeroelastic test rig .
Wind tunnel tests were carried out in an open terrain wind model. A torsional/along-wind frequency ratio of 1.47 and a torsional/cross-wind frequency ratio of 1.41 of the aeroelastic model were adopted. Interference was provided by an identical building located at different positions upstream or downstream of the aeroelastic principal building.
Upstream interference effects in the operating reduced wind velocity range of 5 to 8 were dominated by enhanced turbulence buffeting excitation mechanism. Increases of up to 85% in dynamic responses were measured. For reduced wind velocities near the critical value of about 10, the disturbed wake characteristic of the principal building caused by the highly turbulent region behind the upstream interfering building resulted in considerable decreases in the dynamic cross-wind and torsional responses. When the interfering building was located at the large-separation diagonal region, substantial increases as much as 270% in dynamic responses were recorded due to resonant buffeting.
Downstream interference effects were found to cause a resonant type response on the upstream principal building and resulted in increases of up to 56% in the dynamic responses. This critical downstream interference effect was dependent on the building arrangement and the approach wind speed. However, increased responses were measured only in the operating reduced wind velocity range. At near the critical reduced wind velocity, the dynamic responses decreased significantly.
Dynamic translational responses at the corner of the building were found to be as much as 9.4% larger than those at the centre of the building when the principal building was under critical torsional interference effects with a torsional buffeting factor of up to 1.85 at a reduced wind velocity of 6. However, these increases in dynamic responses were only slightly larger than those in the isolated case which were up to 5.6%. It could be concluded that for the building model tested, the effect of coupled translational-torsional motion caused only slightly-increased resultant displacement responses at the corner of the building and was not generally significant even when the building was subjected to interference excitations.