Wind: Shear wall load
Contents
Concept
Shear wall (wind) load macro allows for automatic calculation and distribution of wind loads on shear walls. The calculation method is based on a Danish practice described in "Betonelementbyggeriers statik" by Jesper Frøbert Jensen. The feature can be accessed from the Load tab > Macro panel.
Requirements
- Only a Plane wall, a Profiled wall or a Timber wall can act as a shear wall. The wind load distribution takes into account only the geometry of the walls (position, length, thickness) but FEM-Design can also handle walls of varying thickness (taking into account the average thickness and the reference plane of the walls).
- Storey system needs to be defined.
Define shear walls
In the Shear wall load dialog, click on Define and then Default settings, where two parameters: Exponent and Alpha, 2, necessary for wall stiffness calculations, can be set. Finally, select the wall(s) that should act as shear load walls.
The two parameters can be later modified using the Properties button.
The stiffness of a wall is calculated according to this formula: Alpha = Alpha, 1 + Alpha, 2 = t * LExponent + Alpha, 2 where: t is the thickness, L is the length of a wall specified as a shear wall.
Note:
- Walls defined as shear walls will change their appearance and will be displayed with a thick burgundy contour (it is an additional layer placed over the original wall).
- The shear wall is placed at the Shear wall layer.
- Walls that were not defined as shear walls, will not participate in the wind load distribution.
Define and generate wind load
There are two ways how to define and generate the wind load on shear walls, differing from each other only by the method of inputting the wind load values.
Manually define the wind load value and generate it in the Shear wall load dialog
After the shear walls are defined, and the correct calculation parameters for individual walls are set, click on the Generate button in the Shear wall load dialog. In the new dialog, the table on the left hand side shows a list of all storeys in the model - here one should input the wind load value corresponding to each storey. After selecting a storey in that table, a list of all shear walls on that storey is listed in the (read-only) table on the right hand side. Here one can verify the pre-calculated stiffness values and position of the shear walls.
At the bottom of the dialog, the wind load directions (x’ and y’) and components (+/-) can be selected to be generated. The wind load is generated automatically by pressing the OK button. The wind loads appear on top of the shear walls as force line loads belonging to the respective load cases that are named: Shear wall load X+/- Y+/-.
Note:
In case of manual definition of the wind load values, it is important to consider the following rules.
- The global coordinate system provides the origin of the wind load coordinate-system.
- The Load generation directions determines only the wind load directions.
- x’p+/- and y’p+/- are measured from the global origin.
If the parameters of shear walls are modified by Properties or the Load generation directions are edited by Modify/Change direction command, wind loads must be generated again.
Automatically calculate the wind load values and generate it in the Regular building (wind load) macro
The Regular building macro is now supplemented with an option to apply the generated wind loads directly on the shear walls defined using the Shear wall load macro. This is sort of a hybrid method, where the program calculates the wind load values, but user decides where they should be applied.
