WIND LOAD CALCULATION
THINGS TO REMEMBER WHILE DESIGNING A STAIR
GENERAL KNOWLEDGE FOR STAIRS DESIGN
February 25, 2019
windload

WIND LOAD CALCULATION ACCORDING TO IS: 875 (PART-3)-1987

WIND LOADS

Wind loads are randomly applied to dynamic loads. The intensity of the wind pressure on the surface of a structure depends on wind velocity, air density, the orientation of the structure, the area of contact surfaces and the shape of the structure.WIND LOAD ANALYSIS STAAD PRO

KEY POINTS

  1. Wind pressure is also known as Air pressure
  2. Wind load is denoted by W
  3. The primary cause of wind is traced to the earth’s rotation and differences in terrestrial radiation
  4. Unit’s wind speed measured in m/s
  5. The wind is generally blowing horizontal to the ground at high wind speed.

DESIGN WIND SPEED

  1. Design wind speed Vz
  2. Vz=K1 x K2 X K3
  3. K1=Risk coefficient
  4. K2=Terrain,height and structure size factor
  5. K3=Topography factor

TERRAIN

The terrain is used to refer to an area of land or type of land when you are considering it is a physical feature.

  • TERRAIN CATEGORIES

Category 1- Exposed open terrain with few or no obstructions and in which the average height of any object surrounding the structure is less than 1.5mExposed open terrain with few or no obstructions

Category 2-Open terrain with well-scattered obstructions having heights generally between 1.5m to 10.Open terrain with well scattered obstructions

Category 3-Terrain with numerous closely spaced obstructions having the size of building structure up to 10m in heights with or without a few isolated tall structures.Terrain with numerous closely spaced obstructions

Category 4-Terrain with numerous large high closely space obstructions.d.	Category 4-Terrain with numerous large high closely space obstructions

THE BUILDING/STRUCTURES ARE CLASSIFIED INTO THE FOLLOWING THREE DIFFERENT   CLASSES DEPENDING UPON THEIR SIZES (K1)

CLASS A-Structures and/or their components such as cladding, glazing, roofing etc having a maximum dimension or less than 20m.

CLASS B-Structures and/or their components such as cladding, glazing, roofing etc.having maximum dimension between 20m and 50m

CLASS C-Structures and/or their components such as cladding, glazing, roofing, etc.having max. dimension greater than 50m.

TOPOGRAPHY(K3)

  • The effect of topography will be significant at a site when the upwind slope is greater than about 3degree and below that the value of K3 may be taken to be equal to 1.
  • The value of K3 is confined in the range of 1to 1.36 for slopes greater than 3degree.TOPOGRAPHY(K3)

RULE OF WIND LOAD APPLY

Building story up to 4 to 5 less is not applied wind load.

  • Column and beam can resistance wind load up to 4 to 5 story building Greater than 4 to 5 story building
  • Will apply wind load because of column and beam, not resistance wind load.

 

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