Compare the overall wind and seismic lateral loads acting up

Compare the overall wind and seismic lateral loads acting upon the building and summarize which case may control the design in a given direction (i.e. wind or seismic in the North-South direction; wind or seismic in the East-West direction).

Solution

Wind Speed- It vries from places to places on the earth surface. There are many factors that effect the wind speed like geographical feature of the place,elvetion, degree of exposure, relation with the near by structures, direction of the prevailing wing,velocity of the prevailing winds,etc. These are mainly the features that are taken into account for the designing of the lateral load of the wind pressure. These calculations are done by assuming that the wind preesure is acting on the roofs and the walls and are static and uniform in nature. These not only disturb the structure constatly but also increases with the increase of the structure height. The loading of the tower can be assumed and cannot be actually calculated.

Earthquake lateral load-It is another live load and is very uncertain.There are 3 types of waves in the earthquake force and the most destructive of them is the Lwave(Love wave) which causes the vibration in the structure in the horizontal direction. The ground below the structure can be shifted to any direction so the designer have to assume almost all the possible direction and design the structure much carefully and the method invoved is the static equivalent load for most of the small and the medium sized buildings.

The wind load is of uniform nature depending upon the the height of the structure and the amount of the surface area that is being covered by the wind.Whereas the earthquake load is more of instantaneous load which depends on the mass of the structure, stiffness of the structure and the acceleration of the ground.

Generally for testing of the structure under wind load and the earthquake load it is assumed that boad loads are not acting together. If the designing is done by the limit state of collapse the coefficient of EQ and wind load is taken as 1.2 & in limit state of seviciblity coefficient is taken to be 0.8.