Data Source page


Property	Description
Data Source	Depending on the National Annex being worked to, there are up to four wind data sources available: BREVe - UK National Grid Ref (only if working to the UK or Ireland National Annex) BREVe - Irish Grid Ref (only if working to the UK or Ireland National Annex) Worst Case Data Data for Each Direction - choosing this option allows you to specify data for multiple wind directions. For further details of the BREVe options, see: Using the EC1991 1-4 Wind Wizard with BREVe data. The remainder of the sections in this topic assume you have chosen to enter the site data manually (either 'Worst Case Data', or 'Data for Each Direction').
Consider Orography	If you select this checkbox, then the orographic data, (manually entered), is used to determine the Orography Factor c_o as clause A.3. When calculating c_alt, the altitude of the upwind base of the orographic feature is used for each wind direction considered. Otherwise the orographic data is ignored, c_o is 1.0 for all heights and c_alt is the same for all directions, using the Site Altitude.
Consider Tall Neighbouring Structures	If the conditions in clause A.4 are met, then the wind loads need to be based on height z_n, see equation (A.14). With this checkbox selected, you are able to enter sufficient data to check if this applies. If applicable, then z_n will be used as the reference height for all wall panels and roof panels in the model. Note: If working to the Sweden NA, Tall Neighbouring Structures are not considered.
Consider Obstructions	With this checkbox selected, the obstruction data, (either defaulted by BREVe depending on the roughness category for the site or entered manually), is used to determine the Displacement Height, h_dis as (A15) in clause A.5. Otherwise the obstructions are ignored and h_dis is taken as zero. Note: If working to the Sweden NA, Obstructions are not considered.
Apply Open Structure Wind Load	With this checkbox selected, additional wind forces are applied to those members, ancillaries and equipment that have the Apply Open Structure Wind Load property selected in their properties. Note: This option is only displayed if at least one entity has been selected to have open structure wind load applied. For more information, see: Open structure wind loads

Clicking Next takes you to the Basic data page below.

Basic data page

This page is used you to define the site details.


Property	Description
Air density	You need to enter air density at the site.
Ground level	If for some reason, the level 0.0m in the Tekla Structural Designer model does not correspond to the ground level, for example a site datum may have been used rather than a building datum, then this field allows you to set the appropriate value so that the reference heights can be calculated correctly.
Fundamental Basic Wind Velocity	Reference should be made to the National Annex being worked to when determining an appropriate basic wind speed. See Clause 4.2 and NA.2.4
Season Factor, c_season	Valid range 0.01 to 10.0 - default 1.0.
Probability Factor, c_prob	Valid range 0.01 to 10.0 - default 1.0.
Default Height for Internal Pressure (z_i)	Clause 7.2.9 (7) implies that all internal pressures should be calculated using a single reference height, (z_i), defaulting to the height of the structure. Leaving Use Building Height checked ensures that the value is automatically updated if the geometry of wall panels or roof panels changes.
Peak Factor, k_p (Sweden NA only)	The Peak Factor was introduced by the Swedish EC NA (EK11) update. Using the default value (3.0) is the equivalent of the old calculation method prior to the update.
Region (Norway NA only)	A Region is needed (Area 1, Area 2 or Area 3) representing three different height zones in the country.
Site Altitude (Norway NA only)	You need to enter the basic altitude that you want to use for the site directly. This is the altitude of your model's base.

Depending on whether you chose worst case data, or data for each direction on the Data Source page, clicking Next either takes you to the Roughness and Obstructions (Worst case) page or the Roughness and Obstructions (Data for each Direction) page.

Roughness and Obstructions (Worst case) page

If you select the Worst Case Data Source, then the next page of the wizard allows you to enter the data for ground roughness and obstructions yourself.


Property	Description
Terrain Category	Reference should be made to the National Annex being worked to when determining an appropriate Terrain Category. Depending on the terrain category selected and National Annex being worked to, you may also be required to enter some of the following data: Average height of upwind buildings, Upwind spacing of surrounding buildings, Upwind distance from sea to site, Upwind distance from edge of town to site.

Depending on your selections on the Data Source page, clicking Next either takes you to the Orography (Worst Case) page, the Tall Neighbouring Structure page, or the Results page.

Roughness and Obstructions (Data for each Direction) page

If you select the Other - Data for each Direction Data Source, then the next page of the wizard allows you to enter the data for ground roughness and obstructions yourself. However, most of the data is then dependent on the wind direction, so you must also make your choice of wind directions on this page.


Property	Description
Direction	Initially there are 4 orthogonal wind directions relative to the Tekla Structural Designer axes, (not geographical North), but you are able to update these using the Dir. buttons and / or changing the direction value as required. (Note: Minimum 1° difference between directions). At least one direction must be defined. Each row of the grid operates in a similar manner to the relevant fields of the Roughness and Obstructions (Worst case) page.

Depending on your selections on the Data Source page, clicking Next either takes you to Orography (Data for each Direction) page, the Tall Neighbouring Structure page, or the Results page.

Orography (Worst Case) page

If Consider Orography was selected, then the next page of the wizard for the Worst Case Data Source allows you to enter the data for orography.


Property	Description
Orographic Feature	Options are: None - no feature, i.e. c_o = 1.0. 2D Escarp - Cliffs and Escarpments, 3D Hill - Hills and Ridges. (See Clause A.3)
Altitude of Upwind Base of Feature, A	This value is used to calculate C_alt instead of the Site Altitude because the Orography is significant. Note: C_alt will be calculated at z_e for each wall and roof panel, not z_s.
Effective Height, H	Effective crest height of the feature. (Figures A.2 & A.3)
Length of Upwind Slope, L_u	Actual length of the upwind slope in the wind direction. (Figures A.2 & A.3)
Length of Downwind Slope, L_d	Actual length of the downwind slope in the wind direction. (Figures A.2 & A.3)
Horizontal Distance to Crest, x	Distance upwind or downwind from the crest to the building site. (Figures A.2 & A.3)
Orography factor, c_o(z) and Turbulence factor, k_l (Norway NA only)	When working to the Norway NA you are not required to enter the above factors; instead you enter the orography factor and turbulence factor directly for the defined 3D or 2D orographic feature.

If on the Data Source page you chose to consider tall neighbouring structures, clicking Next takes you to the Tall Neighbouring Structure page , otherwise it takes you to the Results page.

Orography (Data for each Direction) page


Property	Description
Direction	The wind directions defined on the previous page are maintained and you are not able to update them.
Orographic Feature	Options available are: None - no feature, i.e. c_o = 1.0. 2D Escarp - Cliffs and Escarpments, 3D Hill - Hills and Ridges. (See Clause A.3)
Base Altitude, A	This value is used to calculate C_alt instead of the Site Altitude because the Orography is significant. Note: C_alt will be calculated at z_e for each wall and roof panel, not z_s.
Effective Crest Height, H	Effective crest height of the feature. (Figures A.2 & A.3)
Upwind Slope, L_u	Actual length of the upwind slope in the wind direction. (Figures A.2 & A.3)
Downwind Slope, L_d	Actual length of the downwind slope in the wind direction. (Figures A.2 & A.3)
Horizontal Distance to Crest, x	Distance upwind or downwind from the crest to the building site. (Figures A.2 & A.3)

If on the Data Source page you chose to consider tall neighbouring structures, clicking Next takes you to the Tall Neighbouring Structure page , otherwise it takes you to the Results page.

Tall Neighbouring Structure page

For all methods, if Consider Tall Neighbouring Structure was checked, the penultimate page allows you to determine if tall neighbouring structures affect the design of this structure. (Clause A.4)

Otherwise, the wizard will proceed directly to the Results page and the actual heights of wall and roof panels are used throughout.

The parameters, Height of Tall Neighbour, h_high, Largest Horizontal Dimension of Tall Neighbour, d_large and Distance to Tall Neighbour, x are all as described on Figure A.4 of the code.


Property	Description
Average Height of Neighbours, h_ave	The default is calculated from the BREVe data or the values entered for the Roughness & Obstructions. If Override calculated dimension is cleared, then the value will be updated whenever the wizard is run, otherwise the user-value is used. (Figure A.4)
Height of this structure, h_low	The field is for information only - difference between top of highest wall / roof panel and ground level in the model. (Figure A.4)

Click Next to go to the Results page.

Results page

The final page of the wizard is a summary of the results - peak velocity pressure ranges.

Initially there are 4 orthogonal wind directions relative to the Tekla Structural Designer axes, (not geographical North), but except for the Other - Data for Each Direction method, you are able to update this using the Dir. buttons and / or changing the direction value as required. (Note : Minimum 1° difference between directions). At least one direction must be defined.

You are able to use the <<Details>> button to obtain additional information, including the values of intermediate factors used in the calculations.


Property	Description
Other - Worst Case Data	The calculation of q_p is very similar to the BREVe Method, (see above), except that the worst case data has been entered by you, and this page allows you to enter your own values for C_dir. As there is no data for each 30° sector, the Vortex view only shows the Peak Velocity Pressures calculated for each reference height for each direction.
Other - Data for each Direction	The calculation of q_p is very similar to the BREVe Method, (see above), except that the data has been entered by you for each direction only so a direct calculation can be performed instead of taking the worst case over a range of sectors. Also this page allows you to enter your own values for C_dir. As there is no data for each 30° sector, the Vortex view only shows the Peak Velocity Pressures calculated for each reference height for each direction.

When you click Finish, the wizard generates the wind zones for the entire building for each of the specified wind directions.

Note:

Before moving on you should take a moment to inspect the Wind Model status on the Project Workspace> Status tab, in order to check that no Limitations have been encountered.

Using the EC1991-1-4 Wind wizard with manual data