Past studies have been carried out by researchers with the help of model analysis to get more accurate information regarding wind structure interaction. The predicted wind speed is usually enumerated as the maximum wind speed which is surpassed, on average, once in every N year (return periods) for example, I.S: 875 (Part-3) ( 1987) requires that ordinary structures be designed for an annual exceed probability of 2 % which is equivalent to 50 years of return periods. The precise evaluation of the extreme wind is mainly connected with the quality of statistical data of wind velocity which is associated with performance and calibration of measuring instruments, common averaging time, same height above the ground, roughness of the terrain, etc. In the definition of the overall strength, durability and risk of failure of structures, extreme wind speed is an important factor, mostly reliant on the general weather pattern over many years and local environmental and topographical conditions.
At present, the wind tunnel model experiment and numerical simulation using computational fluid dynamics (CFD) are the available research tools to get deeper insight into the behavior of gigantic structures subjected to turbulent wind load. Simple quasi-static analysis of wind loading, which is globally applied to the design of low- to medium-rise structures, can be unacceptably conservative for the design of very tall buildings. There are several different phenomena giving rise to dynamic response of tall structures under wind such as buffeting, vortex shedding, galloping and flutter. In addition to this, if the plan of the building is unconventional, then wind analysis is a task of great complexity because of the many flow situations arising from the interaction of the wind with the structures. Because of the scarcity of land these days, vertical construction is given due importance and the buildings are much higher than before, making them highly susceptible to horizontal loading like wind load. The magnitude of the moment increases considerably with slenderness, because the moment is proportional to the square of the height of the building, just like a cantilever beam under varying loads. Unsteady vortices are generated in the wake region due to a combination of positive and negative pressure in the windward and leeward faces, respectively.Īs buildings are cantilever structures, there is generation of base moment whenever it is under lateral load. The force coefficient ( C f) along the X direction is extreme for 15° wind angle and along Y direction it is maximum for 60° angle of attack. The nature of deviation of external pressure coefficients along the height of the building as well as along the perimeter of the building for different wind angles of attack is presented. The variation of wind pressure on different surfaces of the building is clearly shown by contour plots. The wind flow pattern around the building showing flow separation characteristics and vortices are presented. Force coefficients both in the along and across wind direction as well as the external surface pressure coefficients for different faces of the object building are determined and listed for wind incidence angle 0°–150° with increment of 30°. For that purpose, computational fluid dynamics (CFD) package of ANSYS is used. The present paper is centered on the study to understand the behavior of various surfaces of a ‘Z’ plan-shaped tall building under varying wind directions.
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