User documentation
This calculation is presented in three layouts – Full, Standard and Brief
Dialogue
National annex selector
Combobox "National Annex" is used for selecting proper annex for calculation of the snow load.
Snow load requires selecion the national annex, because in Standard EN are not defined characteristic values of snow load on the ground.
For explanation of the National annex parameters related to snow load select national annex from the list below.
General properties
General properties are similar to all snow load forms.
Checkbox "Print headline" represent official name for calculation. User can change it by uncheck "Print headline" and check "Print userdefined headline" and write his own headline into appropriate string line.
Checkbox "Print the dimensions of the construction" show/hide calculation of the Dimensions of the construction
Checkbox "Print the calculation of the load at unit lenght of the roof" show/hide calculation of the Load at unit length in the direction of roof
Geometry of the roof
Combo-box "Style of the definition of the roof" is used for selecting the method of definition the roof geometry.
Case "By horizontal distance and height" allow user define widths of both slopes and height from the eaves to the rigde. All three are limited from 0 to 100 meters. Roof slopes are than calculated from the dimensions.
Case "By angles and width of roof" allow user define slopes for the roofs and width of the building. Agles are limited from 0 to 90 °. Width of the building is limited from 0 to 100 m. Width of the slopes are calculated from previously defined parameters.
"Use calculation of shape coefficient according Annex B2" checkbox appear if selected National annex allows using calculation according annex B2 of standard code.
"Number of spans" is used for definituon the number of span on the roof. The value is used in the calculation "Load at unit lenght of the roof".
"Snow fences or other obstruction or parapet on left/right side" checkboxes are used in the calculation of the roof shape coefficients. If TRUE, obstruction exist, snow shape coefficient for that slope μ1(αi) is 0,8. If FALSE slow shape coefficient is calculated.
Parameters of the snow load
These parameters are depended on selected National annex.
Exposure coefficient
These parameters are depended on selected National annex.
Thermal coefficient
These parameters are depended on selected National annex.
Calculation
Dimensions of the construction
Case "By horizontal distance and height":
Width of the first slope, Width of the second slope and Height from the eaves to the ridge is defined in the dialog.
First and second slope are calculated as arctg of the appropriate width and height.
Walley slope is calculated as arithmetical average of both slopes.
Case "By angles and width of roof":
Width of the building, first and second slope are defined in the dialog.
Width of the first/second slope are calculated from the geometry.
Characteristic value of snow load on the ground and Coefficients
These parts of calculation are described in the annotation for Coefficients for the snow load
Shape coefficients
Left and right side shape coefficients are dependend on selected National annex.
If obstruction exist, value of that coefficient μ1(αi) = 0,8.
Ridge shape coefficient is calculated same way as left or right side shape coefficient. Just angle α1,2 is used insdead of α1 or α2.
Valley shape coefficient calculation is defined in table below. However the maximal value μ2 for angle 60° can be defined by National annex. Standard value is 1,6 for angle 60°.
For angles between 30° and 60° is used linear interpolation between 1,6 and value defined by National annex. Standard is 1,6 also.
Standard values are grouped in the table:
| Angle of pitch of roof α |
0° ≤ α ≤ 30° |
30° ≤ α ≤ 60° |
α ≥ 60° |
| μ1(αi) |
0,8 |
0,8•(60 - α)/30 |
0,0 |
| μ2(α1,2) |
0,8+0,8•α/30 |
1,6 |
-- |
Calculation according annex B2 is described in National annex.
Calculation of the snow load
Snow load is calculated in two cases. Undrifted load (Case i) and drifted load (Case ii).
Shape coefficients μ1(αi) and proper snow load coefficients are used for Case (i).
Shape coefficient μ2(α1,2) and proper snow load coefficients are used for Case (ii).
Explanation of symbols
A - Altitude above sea level [m]
b - Width of the building [m]
b1 - Width of the first slope [m]
b2 - Width of the second slope [m]
Ce - Exposure coefficient
Cesl - Exceptional load coefficient
Ct - Thermal coefficient
h - Height from the eaves to the ridge [m]
n - Number of spans
sk - Characteristic value of snow load on the ground [kN/m2]
α1 - First slope angle [°]
α2 - Second slope angle [°]
α1,2 - Valley slope angle [°]
μ1(α1) - Left side shape coefficient
μ1(α2) - Right side shape coefficient
μ1(α1,2) - Ridge shape coefficient
μ2(α1,2) - Valley shape coefficient