*The effect that a seismic action will have in a structure is determined by regarding an earthquake with horizontal design ground seismic acceleration equal to A=α*g*

In the duration of an earthquake, a horizontal seismic force **H** is applied in every mass **M** that has gravity load **W**. The **H** force is equal to a percentage ε of the **W** force. ε value usually varies between 0.00 and 0.50 while in a very intense seismic action it may rise above 1.00.

*In general terms, the distribution of seismic accelerations has the form of a triangle.*

The structure shown above belongs to the Seismic Zone Z1 (seismic ground acceleration equal to 0.16), the mean value of the design seismic acceleration is around 0.12g (ε0=0.12) and the resultant seismic force Fs is around 1400 kN. The theoretical height that this force is applied to, is around the 2/3 of the structure’s total height.

*Comparing the wind and the seismic forces applied to that structure we realize that the wind effect upon the structure is at least four times smaller than the seismic effect*

In the same structure, when placed in a geographical region with intense winds, the mean value of the wind pressure is around 1.50 kN/m² and the resultant force around 400 kN. The total service load applied is 12.000 kN. Therefore the wind force is equal to 0.03% of the vertical loads and its theoretical application area is in the middle of the structure’s height.