AERODYNAMIC STUDY OF TALL BUILDINGS UNDER WIND LOAD

Abstract

With the advancement of technology and enormous growth in population, the need and design of tall structures with different configuration has been a growing trend. High rise structures have always fascinated from the beginning of civilization and are unique in various aspects such as consideration of lateral deflections. High Rise Buildings are cantilever structures subjected to substantial lateral loads and responses. In design of such structures for wind loading, occupant comfort along with serviceability is the dominant criteria along with safety of structure. Wind is a complicated phenomenon in which motion of an individual particle is so unpredictable that one need to be concerned about statistical distribution of velocity rather than just simple averages. The total wind force is equal to the sum of windward pressure and leeward suction, although each has its own local effect. In tall buildings, the aerodynamic and dynamic effects are to be analyzed along with the static effects, whereas in low rise buildings only static effects are sufficient to be considered. Such structures are subjected to along with as well as across wind effects. The along wind effect are caused primarily due to buffeting phenomenon caused due to gust effects whereas across wind induced effects are due to vortex shedding. Galloping phenomenon are more susceptible to structural elements that are not circular, which is due to transverse oscillations of structures due to wind forces that are in phase with motion. Flutter is another unstable oscillatory motion. Eddies of varied sizes and rotating properties make up wind. Wind is turbulent or gusty because of these eddies. Strong winds' gustiness is mostly caused by interaction with surface characteristics at lower altitudes of the atmosphere. The average wind speed during a ten minute or longer period of time tends to rise with height, while the gustiness tends to reduce with height. However, the most common design that is proposed for tall structures are rectangular or square shaped buildings. The design of tall buildings subjected to wind loads does require a deeper grasp of mechanism of loads.