eurocode wind load in open structure.

[ramihabchi]

In eurocode EN 1991-4 in section 7.2.9 about internal pressure it says that if more than 30% on 2 walls are opening area then we design structure under section 7.4 does this means that I consider the envelope walls as free standing walls?and does this rule applies to external pressure as well?
Excuse me if it is a basic question but I am new to eurocode.

 

[HTURKAK]

The snap from the code BS EN 1991-1-4:2005+A1:2010

7.2.9 Internal pressure

....(2) The internal pressure coefficient, cpi, depends on the size and distribution of the openings in the
building envelope. When in at least two sides of the buildings (facades or roof) the total area of
openings in each side is more than 30 % of the area of that side, the actions on the structure should
not be calculated from the rules given in this section but the rules of 7.3 and 7.4 should instead be
used.

and 7.3 for Canopy roofs and 7.4 Free-standing walls, parapets, fences and signboards...

IMO, the code is more than clear and pretty straightforward..

 

[ramihabchi]

Do we consider only wind load cases for each direction normal to the periphery?i cannot find specification on the directions to be considered.

 

[HTURKAK]

Look to the basic wind velocity vb = cdirXcseason X vb,0 and applicable National Annex for cdir.

and ( NOTE 2 The value of the directional factor, cdir, for various wind directions may be found in the National
Annex. The recommended value is 1,0.)..

 

[ramihabchi]

If I understand you correctly the cases of external pressure are the orthogonal 0 90 and 180 degrees directions and if an other direction might have more critical loads it is taken into account by amplification of the orthogonal loads

 

[HTURKAK]

I will not say blindly correct. There are certain cases where the designer should look for critical wind direction and combine the orthogonal effects.

If you provide more detail regarding the structure , applicable annex, you may get better responds ..