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Timestamp: 2020-08-06 21:57:25
Document Index: 372468520

Matched Legal Cases: ['§4', '§4', '§4', '§4', '§7', '§7', '§4']

Calculation of wind pressure loads on flat roofs - Eurocode 1
Eurocode 1 Wind load on flat roofs (external and internal pressure coefficients)
Calculation of wind load action effects on flat roofs (including small parapets). The net effect of external and internal wind pressure for zones F, G, H, I on the roof surface are calculated from the corresponding external pressure coefficients
EN 1991-1-4:2005+A1:2010 Section 7.2.3
Roofs with slope α of -5° < α < 5°, consisting of one skin, on buildings having permanent side walls.
Only countries that adopt CEN recommended values for section 7.2.3 of EN1991-1-4 are supported. The value of the peak velocity pressure can be specified manually. Otherwise automatic calculation of peak velocity pressure is supported, in addition to countries that adopt the CEN recommended values for NDPs, also for the following National Annexes: Finland, Portugal. The National Annexes of Germamy, Norway, Spain, Sweden, Switzerland are NOT supported (enter peak velocity pressure manually).
Hint: Select 'Custom peak velocity pressure' in the terrain category dropdown in order to manually specify the peak velocity pressure.
0 I II III IV Custom peak velocity pressure
The terrain categories are illustrated in EN1991-1-4 Annex A. The transition zones between terrain categories are specified in EN1991-1-4 §A.2.
Illustration of Terrain categories reproduced from EN1991-1-4 Annex A
The basic wind velocity is given as vb = vb,0⋅cdir⋅cseason where the fundamental value of basic wind velocity vb,0 is defined in EN1991-1-4 §4.2(1)P and its value is provided in the National Annex. Altitude correction may also be specified in the National Annex for EN1991-1-4 §4.2(2)P. The directional and season factors are generally cdir = 1.0 and cseason = 1.0. For particular cases values smaller than 1.0 may be specified in the National Annex for EN1991-1-4 §4.2(2)P.
Peak velocity pressure at reference height
qp(ze)
Dimension of rectangular plan parallel to the wind direction
Dimension of rectangular plan perpendicular to the wind direction
Height of building from ground up to roof level
Additional height of parapets
Size of loaded area that produces the wind action for the examined verification
>10m² (Cpe,10) <1m² (Cpe,1)
Local coefficients cpe,1 are intended for design of small elements and fixings with an area per element ≤ 1 m2 (e.g cladding elements, roofing elements). Overall coefficients cpe,10 may be used for the design of the overall load bearing structure with loaded area ≥ 10 m2.
Orography factor at reference height ze
c0(ze)
Orography factor larger than 1.0 may be applicable over isolated hills and escarpments. See EN1991-1-4 §4.3.3 and §A.3 for more details.
Minimum value of internal pressure coefficient
cpi,min
Minimum value of internal pressure coefficient cpi to be used when unfavorable. For buildings without a dominant face and where it is not possible, or not considered justified, to estimate ratio μ the value cpi = -0.3 may be used. Otherwise more accurate value may be determined in accordance with EN1991-14 §7.2.9. Enter cpi,min = cpi,max= 0 to ignore internal pressure.
Maximum value of internal pressure coefficient
cpi,max
Maximum value of internal pressure coefficient cpi to be used when unfavorable. For buildings without a dominant face and where it is not possible, or not considered justified, to estimate ratio μ the value cpi = +0.2 may be used. Otherwise more accurate value may be determined in accordance with EN1991-14 §7.2.9. Enter cpi,min = cpi,max= 0 to ignore internal pressure.
According to EN1991-1-4 §4.5(1) and the National Annex.
1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.194 1.25 1.25 1.25 1.2 1.226