Orography is the study of mountains, hills, escarpments and any part of a region's elevated terrain. It is important to study the orography of the project site since the wind velocity can accelerate towards a crest. In ESICS the orography of every twelve directions is analyzed in accordance with section A.3 of Eurocode. Note that the orography is significant if the structure falls in one of the shaded areas demonstrated in Figure 8 in any of the twelve directions.
Figure 8. Definition of significant orography in accordance with BS EN 1991-1-4:2005
Orography properties in each direction are automatically detected by ESICS. The results can be found in the "Orography Properties in Each Direction (Automatic)" table that is only visible in the detailed mode. Figure 9 is a snip-it of the "Orography Properties in Each Direction (Automatic)" table for a site located in Crowden, High Peak borough of Derbyshire, UK.
Figure 9. Snapshot of the "Orography Properties in Each Direction (Automatic)" table for a site located in Crowden, High Peak borough of Derbyshire, UK.
If the ESICS automatic values are not to the user's satisfaction the details of the relevant orography can be entered in the "Orography Properties in Each Direction (Manual Override)" tables, overriding the automatic values. In these tables, each direction refers to the direction from which the wind is blowing. Also, the length of the downwind slope is only relevant for hills or ridges; it may be ignored for escarpments.
Note that these values are used for calculating the Orography Factor Co, in accordance with the numerical calculation of orography coefficients in section A.3 of Eurocode.