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-EN 1991-1-3+C1+A1:2019/NB:2019 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 |
| hnd (lowest point discharge), [m] | Height of discharge above the roof or the height of the eaves: dhw (x=0) = dnd + hnd | |
| Position main structure |
| 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 γM | The model factor is used for the iterative calculation of the rainwater load according to the NEN-EN 1991-1-3-C1+A1:2019/NB:2019#7.2(7), reducing the structure stiffness by the default value of γM = 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 |