Wind Storm Research Paper

WIND ENGINEERING

I. INTRODUCTION

Environmental loading such as wind and seismic both competes as the dominant effect load on structures. Both loadings produced almost equal amounts of damage on structures over a long time period, although strong and large damaging earthquakes occur less often than severe wind storms. Severe wind storms happens almost every day of the year somewhere on Earth – although some storms are small and localised. In some tropical countries, the most severe of all wind events generated are the tropical cyclones (which includes hurricanes and typhoons). Devastating effects will happen if these storms make landfall on populated areas.

Effects of wind on structures can be static, dynamic and aerodynamic. In general, static

It is actually an air movement relative to the Earth, driven by several different forces, especially the pressure differences in the atmosphere, which are themselves produced by some differential solar heating of the different parts of the Earth’s surface and also, the forces generated by the rotation of the Earth. Differences in solar radiation between the Equator and the poles produce pressure and temperature differences. These together with the effects of the Earth’s rotation set up large-scale circulation systems in the atmosphere, with both horizontal and vertical orientations. The result of these circulations is that the prevailing wind directions in the tropics, and near the poles, tend to be easterly. Westerly winds dominate in the temperate

For dynamically sensitive buildings and other structures, a gust effect factor, Gf, is given. The formulation of gust effect factor, Gf, is primarily for buildings; it is not always applicable to other structures. It should be noted that the gust effect factor, Gf, is based on along-wind buffeting response. Vortex shedding can be present with bluff-shaped cylindrical bodies. It can become a problem when the frequency of shedding is close to, or equal to, the frequency of the first or second transverse modes of the structure. The intensity of excitation increases with aspect ratio (height-to-width or length-to-breadth) and decreases with increasing structural damping. Structures with low damping and with an aspect ratio of 8 or more could be prone to damaging vortex excitation. If across-wind or torsional excitation appears to be a possibility, expert advice should be