Introduction Wind is essentially the large scale Horizontalmovement of free air. It plays an important role indesign of tall structures because it exerts loads onBuilding. High Rise Building-A building Having height more then15m As per National Building Code 2005 of India iscalled High Rise Building.Imperial Tower 1(254m)Ref- Wikipedia
What is Wind?Wind means the motion of air in the atmosphere.The response of structures to wind depends onthecharacteristics of the wind.
Causes of Wind- Wind is caused by airflowing from highpressure to low pressure.Since the Earth is rotating,however, the air does notflow directly from high tolow pressure, but it isdeflected to the right (in theNorthern Hemisphere; tothe left in the SouthernHemisphere), so that thewind flowsmostly around the high andlow pressure areas.
Variation of Wind Velocity withHeight-Near the earth’s surface, the motion isopposed, and the wind speed reduced,by the surface friction. At the surface,the wind speed reduces to zero andthen begins to increase with height,and at some height, known as thegradient height, the motion may beconsidered to be free of the earth’sfrictional influence and will attainits ‘gradient velocity’.Gradient Height 300 m for flat ground& 550 m for very rough terrain
How wind force governing for tall structure?with increase height of building•Construction cost per unit area decrease•Increasing lightness in weight per unit area•More danger against high velocity of wind forceat high level.
Wind Effects on StructuresWind effects on structures can be classified as‘Static’ and ‘Dynamic’.Static-Static wind effect primarily causeselastic bending and twisting of structure.DynamicFor tall, long span and slender structures a‘dynamic analysis’ of the structure is essential.Wind gusts cause fluctuating forces on thestructure which induce large dynamic motions,including oscillations.
Different Forces On Structural element of Building -
Variation of wind pressure with Height of building-
Determination of Wind Loads as per IS 875 (Part 3)Physical parameters-•Length : 17m•Width : 13m•Height : 20.5m•Height of each storey : 3mWind Data-•Wind Zone : 2(Basic wind Speed= 39m/s ForRaipur)•Terrain Category : 3•Class of Structure : A (Since Max. Dimension is lessthen 20m)•Topography : Flat that is upwind slope <3 °•Life of Structure : 100 Years3d Model By
Design wind speed –Vz=Vb.K1.K2.K3Vz = Design wind speed at any height z inm/s;K1= Probability Factor (K1=1.06 ForImportant Buildings of Life 100 years)K2= Terrain, Height and Structure sizefactor (Varies for Height)K3= Topography Factor)
Main ConclusionsIn the Static Analysis of the RCC Building thecomparison has been made in two cases in first case withoutconsidering the wind load and Considering the wind load insecond case. Results from SAP2000 Shown that the Bendingmoment and shear Force increase due to wind load hencewind load governing factor for design of High rise building .
•http://en.wikipedia.org/wiki/The_Imperial_(Mumbai)References•http://www.weatherquestions.com/What_causes_wind.htm•IS 875-Part3 ( 1987) Indian Standards Code of Practice for Design Wind Loads.•Special Publication of BIS SP64 Wind Load Explanatory Hand Book .•Wind And Earthquake Resistant Buildings Structural Analysis And Design By Bungale S. Taranth.