General

Adding rainwater loads

Adding rainwater loads is an iterative process based on the displacement due to Dead Load combined with the amount of water related to one permanent lowest point discharge.

The method of calculation is based on the NEN 6702#8.7.1 by:

EN 1991-1-6 #4.9 (7):

(7) Actions from rainwater should be taken into account for conditions where there may be collection of water such as ponding effects from, for example, inadequate drainage, imperfections of surfaces, deflections and/or failure of dewatering devices.

NEN-EN 1991-1-1:2002/NB: 2006: 6.3.8 Loads induced by rainwater on flat roofs:

(1) Loads induced by rainwater on roofs shall be taken from 8.7.1 of NEN 6702.

Selection

Rainwater loads are added on preselected members: "Add rainwater on selection members". If no members are selected in combination with horizontal beams at highest point level, these members will be considered as a sub selection set: "Add rainwater on flat roof". In other cases no rainwater will be added.

Properties

Properties	Definition	Comments
b or d (size discharge), [m]	Relative width/discharge diameter, dependent on the system size of the structure. For example: when the length of the roof-surface with a discharge is 20 m and the total width of the discharge is one meter. With a system size of five meter the width of the discharge that should be entered will be 1/20*5=250 mm (for every pattern lines)	In case of a pitched roof and in situations in which a camber (with a flat roof) is applied, it is assumed that the registered discharge accounts for the entire (selected) roof, so the water will be on all sides
h_nd (lowest point discharge), [m]	Height of discharge above the roof or the height of the eaves: d_hw (x=0) = d_nd + h_nd
Position main structure	2D system; the structure "as-is"; no 3D effects 3D syst., 1 field; incl. 3D effects for frame with one pattern lines 3D syst., end field; incl. 3D effects for a frame with several pattern lines, in which the end field will be considered 3D syst., inner fields incl. 3D effects for a frame with several pattern lines, in which the inner field will be considered	3D effects can only be taken into account for flat roofs
Structure system size, [m]	System size main structure
Ref. points number	Number of reference points for calculation accuracy of loading structure
Camber, [m]	Camber in the center of the selection; additional deformation is constructed triangularly. Camber (upwards) is positive
Slope, [%]	If the roof has been modeled under slope it will be considered in the calculation automatically and it is impossible to enter a slope	Camber and slope can be combined
Slope side highest point	Selection: left- or right side of the selection
Reference period	Reference period for calculation of rainfall intensity according NEN-EN 1991-1-3+C1+A1#7.2(4)
Model factor γ_{_M}	NEN6702#8.7.1.4: The bending should be calculated as the bending in a final position according to 10.1, in which the first load should be considered the load resulted from the water level according to 8.7.1.5. and in which the stiffness of the building structure is divided by γ_{_M} = 1,3
Internal results	Option to save all intermediate steps from the iterate process as a load case in the load sheet. It shows the course of the increase of water during the years