IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 5 Ver. I (Sep. - Oct. 2015), PP 14-21 www.iosrjournals.org DOI: 10.9790/1684-12511421 www.iosrjournals.org 14 | Page Aerodynamic Studies of non – Circular High – rise buildings Yechuri N V Mani Sandeep Kumar 1 , V Dhana Raju 2 , P Ravindra Kumar 3 1, 2, 3 (Department of Mechanical Engineering, Lakireddy Balireddy College of Engineering, India) Abstract: Wind induced load is an important issue for tall buildings, cable suspension bridges, electricity transmission towers, telecommunication towers and chimneys during natural disasters like strong winds of cyclone and earth quakes. One way to minimize wind-induced vibrations of tall buildings is to focus more on their shapes in the design stage. Important design aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind responses, which is a key issue in tall building wind-resistant design. Four models of non-circular high rise buildings were made and tested in a low speed wind tunnel. Triangular, taper square, square steps with sharp corners and square steps with filleted corners models are prepared. The study investigates the drags force and pressure distribution at the center of different models at different velocities with different orientations. Key words: co- efficient of pressure, Drag force, high –rise buildings, Torsional Vibrations, Wind Tunnel. I. Introduction A tower block, high-rise building, is a tall building or structure used as a residential and/or office building. In some areas they may be referred to as "MDU" standing for “Multi Dwelling Unit”. High–rise structures pose particular design challenges for structural and geotechnical engineers, particularly if situated in a seismically active region or if the underlying soils have geotechnical risk factors such as high compressibility or bay mud. Studies are often required to ensure that pedestrian wind comfort and wind danger concerns are addressed. In order to allow less wind exposure, to transmit more daylight to the ground and to appear more slender, many high-rises have a design with setbacks. Tall buildings have been traditionally designed to be symmetric rectangular, triangular or circular in plan, in order to avoid excessive seismic-induced torsional vibrations due to eccentricity, especially in seismic prone regions like Japan. However, recent tall building design has been released from the spell of compulsory symmetric shape design, and free-style design is increasing. Wind-induced load is an important and essential design issue for tall buildings, cable suspension bridges, electricity transmission towers, telecommunication towers and chimneys. For real structures, the flow field is very complex in nature; hence, experimental studies are mandatory. So far, some studies on the effect of increasing number of sides on aerodynamic characteristics have been conducted, but in the studies only mean drag force has been focused on by the numerical simulations under a uniform flow, no discussions were found on the characteristics of other wind force components and responses using a boundary layer flow. Tamura et.al, 2010 [1], the present trend towards design of tall buildings is toward unconventional shapes such as square cross sections with different helical models as this provides good aerodynamic characteristics. Many researchers have tested wind pressures on irregular plan buildings Anim and Ahuja, 2008 et. al, [2], different rectangular cross sections tapered building models with taper ratios of 5% and 10%, and building models with set-back at mid-height Kim and Kanda, 2010 [3]etc., but, there have been very few studies on triangular cross-section tall buildings. The effects of building plan shape on aerodynamic forces and displacement response have been studied for super-high-rise buildings with square and triangular cross-sections with corner modifications Hayashida et.al. 1990 [4]. Aerodynamic modification of building shape, such as by changing the cross-section with height through tapering, alters the flow pattern around tall buildings, which can reduce wind-induced excitations of buildings with different rectangular cross-sections Lin et al., 2005 [5], tapered building models with taper ratios of 5% and 10%, and building models with set-back at mid-height Kim et.al., 2010 [6].