Abstract
Introduction
The interaction between high-rise buildings and wind force is very complicated. While wind flows through buildings, because of the fluid velocity, the turbulence intensity and the vortex shedding generated downstream, the structures may experience different kinds of vibrations. In addition,the vibrations of the structures may further affects the nearby wind field which also changes the wind induced pressure on the structures, and hence the responses of the them. This coupling effect is called the aerodynamic effect. In order to systemically investigate this complex behavior, this research was focused on the effects of the height and corner shapes to the drag and lift coefficients.
II. Research Methods
This research was majorly based on the wind tunnel test. The models employed were of 6 different corner shapes as well as round and square. The height/width were 4 and 8. The Reynolds number were from 3.5*104 to 1.9*105. The tests were carried out in the first test section of the ABRI wind tunnel. The incoming wind flow was uniform.
A 6 component force balance was employed to measure the wind forces of the models. A ScaniValve system was also used to measure the surface pressure of the additional square and round models for the data comparison.
Finally, the obtained data was mathematically analyzed and the results were compared with the building codes.
III. Conclusions
i. According to the test results, the drag coefficients and the lift coefficients of the square tubes were smaller than those derived from the building codes. Since the test was held in the uniform flow, therefore, the codes can be inferred to be more conservative.
ii. The corner modification can all reduce the drag force and the across wind force. The round corner shapes were more effective than the cut corner shapes. With the distance of the modification getting longer, the difference became smaller. This can be explained that both the modifications became approximate to circular.
iii. Under the same Reynolds number, the drag coefficient and the lift coefficient of the models with the aspect ratio of 4 were smaller than those with the aspect ratio of 8. This implies that the three dimensional effect was more obvious on the shorter models.
IV. Suggestions
1. Immediately applicable:
Develop a data base of the test data for more corner shaped models under different flow fields. Proceed the accuracy and reliability analysis.
Host Agency：ABRI
a. More different shapes should be included to enhance the data base.
b. Tests in the turbulence flow and/or with the atmospheric boundary layer should be conducted to simulate the real wind flow of the buildings.
iv. Future applicable：
Consider the wind flow of Taiwan and revise related current codes.
Host Agency：ABRI
a. With the accumulation of the test data, the empirically equations should be statically derived.
b. Considering the wind data of Taiwan,the current codes can be revised based on the derived equations.