Wind Load (Automatic) – Regular building

Default Short CommandLWINDR

Two types of wind load can be generate in FEM-Design, Regular building and Generic building wind load.

1582804849244-917.pngRegular building wind load generation needs storey-system in the project!

Definition steps

  1. Entering to “Load” mode, the program displays the so-called “main directions” of the current project. These main X’ and Y’ load directions are used by the automatic wind and deviation load definition. By default, the main X and Y load directions are parallel with the Global X and Y axis directions. Set the required load directions for the wind (and deviation) loads with the Change direction command (Modify menu).
    1582804849244-917.pngThe symbol of the main load directions are stored on “Main directionsObject layers
  2. Start the 1583331521678-422.png  Wind load command from Loads tabmenu.
    1582804849244-917.pngThe generated wind line loads will be inserted in a load cases called “Wind load X” and “Wind load Y”. If there are no same named load cases in the project, the program automatically defines them for the automatic wind load components.
  3. Set the wind speed and terrain type in the settings dialog according to the building environment. The program calculates the applied wind load values by the levels of the current project’s storey-system from the given parameters and the model size set at the Storey command (horizontal building size and story level heights). The calculated intensity values are displayed in table format (right part of the dialog).
  4. Set the wind load X and Y directions same add or converse (–) with/to the main X and Y direction system.
  5. Clicking OK generates line loads in the external edges of plates that are located on stories surfaces/region parts.
1582804849244-917.pngWhile generating Wind Loads all existing Wind Loads are redefined! That may delete previously defined Wind Load cases.

Wind load (Automatic) - Generic building


Default Short CommandLWINDG

Generic building’s wind load (as surface loads) can be placed automatically on covers.

  1. Set the type of the cover according to EC: External wall 1583335189376-724.png , Flat roof 1583335200236-761.png , Lean-to 1583335218775-449.png or Ridge-roof 1583335228704-815.png :
    Figure: Generic building wind load dialog

    In all four cases a green arrow plays a crucial role in correct load generation. In Lean-to and Ridge-roof the arrows are generated automatically by FD, but for flat roof and external wall, the user has to define it. Details can be found in the sections below.

    The importance of the green arrows can be understood at the bottom-left figure in the four settings windows of the four cover type, showing the wind direction terminolgy of EC. In the standard, if the deviation of wind speed is in the range of +45° and -45°, it is taken as 0°. In the range of 45°-135°, it’s taken to be 90°, between 135°-225°, to be 180°, and in the last interval to be 270°. By this assumption, no other direction can be imagined as the four cases in the window below, which shows the Default Settings (the button shown in the figure above) for external wall first, and the others next.

    External wall

    After having chosen 1583336451420-188.png, this is what you get in Default settings:

    Figure: External wall dialog
    The figure at bottom-left shows the direction terminology. For 0°, you can scroll down the typical cases mentioned by EC:

    and for 180°:
    Figure: External wall – setting multiplication factor for predefined wall positions

    By choosing the one valid for the current cover, the multiplication factor will be adjusted to the right value. For more sophisticated cases you have the possibility to define the multiplication factor manually.

    If the wind direction is in the plane of the wall, some more highly loaded zones (A and B, see EC 1-4 for details) are applied by EC at the leading edge of the wall for taking the effect of turbulence into account. Followed by zone C, a less loaded domain. If no turbulence can be imagined at the leading edge, you can cancel out the creation of zone A and B (The legend in bottom left helps in understanding the directions.):
    Figure: Wind load direction terminology

    EC allows the division of the load domain into horizontal stripes, so you may take into account the height dependence of wind velocity by the application of several horizontal stripes:

    Figure: Wind load vertical distribution

    In case of external wall, you have to select the cover by clicking on it, and than select a point at the external side of the building. The green label, and also the arrow will appear, but the arrow will be perpendicular to the plane of the cover. If you have a composed building like in the case below, you can unify several wall covers by pushing Ctrl, and selecting the members:

    Figure: Selecting External wall

    If you have selected one element, you can immediately define the green arrow by picking an external point, in case of more elements you have to end the selection by ’Enter’, and then point an external point outside the walls:

    Figure: Defining wall’s external point

    The wind load generated according to EC will consider the unified green rectangle as one surface.
    1582804849244-917.pngAfter classified all the walls, verify all arrows’ pointing out from the building in order to obtain well directed wind loads on the walls.

    Flat roof
    In case of Flat roof 1583336989503-529.png, the following appears:
    Figure: Flat roof dialog
    In the bottom left, the figure shows the notation of the directions with respect to the green arrow. The user can switch on or off the creation of the turbulence zones like in the case of External wall, and also can change the multiplication factors manually.

    If an attic wall is at the edge of the cover, the height is required, as it has influence on the values of the load.

    After choosing the settings, you have to click on the cover, and then, you have to give the main direction for wind generation:

    Figure: Defining the main direction for wind generation

    After the definition of the direction a green label will appear with an arrow in the middle of the cover. If possible, you should choose a main direction of the building that coincides with axis X, for obtaining the correct distribution in the different wind load cases.

    1582804849244-917.pngAn incorrectly defined direction can lead to false wind load distribution.

    You can modify its direction in Modify>Change direction.  (If the label or the arrow is missing after creation, try another graphic engine in Settings>All>Environment>General>Graphic Engine)


    In case of Lean-to 1583337261908-549.png, the dialog window is as follows:
    Figure: Lean-to dialog

    Likely to former cases, the notation of EC appears at bottom-left corner. If you have a cover that is not parallel with the load coordinate-system, the wind load directions will fit the cover’s direction.  The different factors can be set eiter by scrolling down the  symbol:

    1583337334941-898.png and 1583337363877-545.png
    Figure: Lean-to – setting multiplication factor for predefined wall positions

    or, by setting them manually.

    If required, turbulence zones can be switched off:

    Figure: Turbulence zone application

    Ridge roof
    The pop up window in case of Ridge roof:
    Figure: Ridge roof dialog

    Likely to former cases, the notation of EC appears at bottom-left corner. If you have a cover that is not parallel with the load coordinate-system, the wind load directions will fit the cover’s direction. The different factors can be set either by scrolling down the symbol:
    1583337505651-663.png and 1583337517765-600.png
    Figure: Ridge roof – setting multiplication factor for predefined wall positions

    or, by setting them manually.

    If required, turbulence zones can be switched off.
    Figure: Turbulence zone application

  2. Generate the wind load

    When clicking on the symbol 1583337629109-923.png , the wind generation tool window appears:
    Figure: Wind load generation dialog

    In this window you have to classify the building according to EC, and give  the basic wind velocity  for load generation.

    After clicking OK, the wind loads are generated in 16 different load cases:

    Figure: Automatically generated wind load (WL,Y-,1)

    (For proportional displaying of loads click: Settings>All>Display>Load>Display proportionally) In the example above, WL Y-, 1. is active which corresponds to a wind marked by the orange arrow.

    It is parallel with the loaded wall, and as it is in the range of 45°-135°, according to the load’s coordinate system, it is stored in WL, Y-, 1. For each (four) directions, generally 4 different cases can be imagined in EC (because of variation of suction and pressure), but they not necessarily vary: in the case above, all four versions of WL, Y-, are the same for the loaded external wall.

    1582804849244-917.pngAccording to EC, protruding parts of roofs should be loaded at underside with the pressure applied on the wall below. This is not taken into account by the wind loading module of FD 11.0.

    If the building have a frequently used shape, the program generates the different load domains and the values will be applied on them automatically.

Created by Fredrik Lagerström on 2020/04/02 18:13
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