BS6399-2 Wind Modeller Quick Start Guide

CSC Fastrak ™

Structural steelwork analysis and design

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QUICK START GUIDE BUILDING DESIGNER

Building Designer Documentation page 2

Friday 1 September 2006 – 08:56

Table of Contents


Chapter 1

Introduction

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Chapter 2

Application of the BS:6399 wind module to a structure. .

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Chapter 3

Application of roofs to the model.

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Chapter 4

Application of Walls to the model

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Chapter 5

Wind Definitions for Roofs and Walls .

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Chapter 6

Wind Module .

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Chapter 7

What Next?

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Chapter 8

The Wind Modeller Quick Start Guide Continues

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E:\CSC Doc\Building Designer\Quick Start Guide\Wind Modeller Quick Start GuideTOC.fm



Table of Contents

Chapter 1 : Introduction

Chapter 1


Introduction Fastrak Wind Modeller is design software which allows you to load a Fastrak Building Designer model for wind in accordance with BS6399-2:1997. The wind load assessment is performed on the walls and roofs which are applied to your building model. The resulting wind loads are distributed back to the members for structural analysis and design. You can use Fastrak Wind Modeller: • to determine site effective wind speeds (standard or directional),

• • • • •

to determine zone wind pressures on walls and roofs, to determine standard values of Cpe for each zone, to determine wind pressures on each zone, to determine wind loads and loadcases/ combinations for your structure, to links with the wind UK BREVe database.

Fastrak Wind Modeller is a very powerful tool which has been developed to aid engineers in their assessment of wind loading on a building. You will find that the determination of the wind speeds, the pressures and the zones is rigorous but the final wind loads adopted are your responsibility. The aim of this document is to enable you to become productive with Fastrak Wind Modeller as quickly as possible. For further information you should look at the Fastrak Wind Modeller Engineer's Handbook which is installed in the Documentation folder which you will find within the folder to which you installed your Fastrak products.

1.1

BREVe Copyright BRE and Nicholas J Cook have developed the computer program called BREVe2 designed as an aid to the use of BS 6399-2:1997. © 2000 Nicholas J Cook © 2000 Building Research Establishment Ltd.

E:\CSC Doc\Building Designer\Quick Start Guide\Wind Modeller Quick Start Guide.fm


Chapter 2

Chapter 2 : Application of the BS:6399 wind module to a structure.

Application of the BS:6399 wind module to a structure.

2.1

The Structure

2.1.1

Isometric View

North-West Isometric View

2.2

Design Data

2.2.1

Tutorial Building Description The building used in this Quick Start Guide example essentially consists of two rectangular composite floor areas with a sloping roof system. The floor-to-floor height of the multi-storey structure is 3.5 metres, with a lightweight roof construction. All beams (except the transfer beam at the first floor and the flat roof at the second floor) are of composite construction.

2.2.2

2.2.3

Wind Loading Information •Location •OS Grid Reference •Maximum Building Height •Ground Level In Fastrak Model •Building Orientation to North

= Leeds = SE298339 = 13.5 metres = 0.0 metres = 180 degrees

Dynamic Augmentation Factor You must manually perform the dynamic classification of the building, evaluating it in accordance with Clause 1.6.1 and Figure 3 of BS6399-2:1997. If the model created falls beyond the limits of Figure 3, then the building should be assessed using established dynamic methods. This Quick Start Guide example meets these requirements.


Chapter 2 : Application of the BS:6399 wind module to a structure.

2.2.4


Building Shape Assessment. Clause 1.1 of BS6399-2:1997 states that specialist advice should be sought for building shapes that are not covered by the standard (BS6399-2:1997). This Quick Start Guide example is covered by the code.



Chapter 3

Chapter 3 : Application of roofs to the model

Application of roofs to the model 1] Open the prepared model Wind QS Start.fastrak which you will find in the \Documents and settings\All Users\Shared Documents\Fastrak\Examples folder.

Note

Before you use the wind module we advise you to perform a gravity design for the model.

The model just opened has almost completed its gravity design, the final stage is to provide the lightweight roof and roof loading to the structure. 2] Open the 3D Structure view and view it from the South-East.

3.1

Saved files As we created this extension to the worked example we saved the model away at the start of each chapter1 and numbered these saved models according to the chapter number. Thus if you want to pick the example up at a particular point, rather than working through it in its entirety, you can simply open the appropriate file. If you want to load the example as it stands at this point (the start of chapter 3), then the file you need to open is Wind QS Example 03.fastrak, if you wanted to open the example as it stands at the start of chapter 8, then that’s in the file Wind QS Example 08.fastrak and so on. You will find these files in the \documents and settings\All Users\Documents\Fastrak\Examples folder. You can open and use these files, but you can not save them away unless you change their names, this is done to protect the originals.

3.2

What Are Roofs? Roofs (comprised of roofing elements) allow the decomposition of wind loading to the surrounding structural elements in a single span direction. You place these roofing elements in either horizontal or sloping planes. In either case the roofing elements must have structural elements in the direction of the roof span to decompose the load. In order to get the best results from Fastrak Wind Modeller, it is essential that the largest planar surfaces possible are

Footnotes 1. Starting with chapter 3 which is where the example proper starts.




defined as single roof elements. You place roofing elements in your structure by selecting the individual node points which define the roofing element in sequence. To complete the roofing element you pick the initial point that you used again. Note

3.3

Roofs do not add extra load or stiffness to your model and do not create diaphragm action.

Applying roofs to the model 1] Use View Options to ensure that roofs and roof span directions are shown in the

graphical display.

2] In Fastrak Building Designer select Create and Roofs.

3] Now, in sequence, select the points in the structure which define the plane of

the roof element (as shown below). Third click Second click Fourth click

First click and final click to finish

Note

You can either double click the 4th node or click the first node again to place the roof element.




When the roof element is defined its span direction is shown. There are two different sloping roof angles, therefore 2 separate roofing elements are required

3.3.1

Changing the roofing span direction The roofing element as initially created has the wrong span direction. To change the span direction, you need to select the roofing element and change its span direction using the Properties window. 1] Pick Select and Roofs.

2] Select the roofing element you have just added to your model. Then use the Properties pane to alter the span direction.

Note

You can select several roof elements at once and change all their span directions simultaneously.

3] Once you have changed the span direction of the roof element clear its

selection.




4] Place the rest of the roof elements on the structure as shown below. Please

take care to define them with the span directions shown.

South-East Isometric View

Note

3.4

The view above was created using the “Sub-Structure” command.

Application of Area Loading to Roofing Elements To complete the gravity design for the model, you must apply the gravity loading to the roof. •Roof Dead Loading = 0.4 kN/m2 (on slope)

•Roof Imposed Loading = 0.6 kN/m2 (on plan) (Display Adjusted) 1] Load the roofing elements with the appropriate Dead and Live loading, applying this using Area Loads.



3.5


Flat Roofs and Slabs The example used in this Quick Start Guide contains a flat roofed area formed with simple beams (arrowed below). This area needs to have a roof applied with the same loads as previously stated.

1] Use View Options to ensure that slabs and slab span directions are not shown in

the graphical display. Otherwise the slab will obscure the roof graphically. 2] Select Create and Roofs.

3] Select the nodes in sequence and place a roof element over the horizontal area

as shown below, ensure that it spans in the direction shown.

4] Use the previous method to apply the Roof Dead and Roof Imposed loading to

this area.



3.6


Creating load combinations The combinations for Ultimate Limit State, including the Notional Horizontal forces in all directions have already been defined within the model. These include the roof dead and live loadcases.

The gravity loading to the sloped roof areas has also been completed.

3.7

Validation and design 1] Validate the model, then run the Design.

All of the members are in check mode so the design will be quick. The structure should pass all the design checks successfully.



Chapter 4 4.1

Chapter 4 : Application of Walls to the model

Application of Walls to the model

What are walls? Walls are vertical panel elements that can be placed into your structure to allow the decomposition of wind loading in a singular direction. Walls allow a magnitude of area loading to be decomposed as nodal loads back to beam, column and truss member intersections. The wall panel must have structural elements in the direction of the wall span to decompose the load. Walls will act in the same manner as roofs when used in the BS:6399 wind loading module in that the direction of wind will allow automatic zoning of the structure when the wind is applied. In order to get the best results from Fastrak Wind Modeller, it is essential that the largest planar surfaces possible are defined as single wall elements. Note

Walls do not add extra load or stiffness to your model and do not cause diaphragm action to occur.

To place a wall element in your model, you must select its nodes in sequential order.

4.2

Applying walls to the model 1] Use View Options to ensure that walls and wall span directions are shown in

the graphical display.

2] Select Create and Walls.

3] Ensure that you are in the Structure window and view the model from the

South-East so that you see it as shown below.




4] Select node points 1 to 7 as indicated below to place the wall panel. 4 3

2

5

1 and 7

6

Note

You can either double click the 6th node or click the first node again to place the wall element.

You will see that the wall shown below is added to your model.

4.2.1

Changing the wall span direction The wall element displayed above has the correct span direction. If you needed to change the span direction you would need to select the wall element and change its span direction using the Properties window. 1] Select Select and Walls.




2] Select the wall which you have just created and look at the Properties pane.

3] Leave the span direction for the wall at its current setting of 0 degrees. 4] Clear the selection of the wall.

4.2.2

Problems encountered placing walls There are a few issues of which you need to be aware when creating walls. We shall look at these now. 1] Pan and zoom the view to see the area shown below.

In this more complex arrangement of beams (a transfer area) a wall spanning in a horizontal direction is not supported along the edge by a structural object. In this case a you need to add a dummy member in the direction of the wall’s span and you need an extra support at the base to carry this member. In this area you must span the walls vertically since adding the dummy column will also provide support for the transfer beam which is incorrect.



4.2.3


Applying Dummy Members and Extra Supports. 1] In View Options use the Grids page to show the model’s Axis information.

You can use the grid line intersections to place a support. 2] Select Create and Supports.

3] Place a support at the grid line intersection indicated above. Then turn off the

grids.




4] With the support in place, create both walls, ensuring that they span

vertically.

5] Ensure that you clear the selection set of walls

Finally a you will have to place dummy members so that the wind load will decompose. 6] Create the following Beam Dummy Member attribute set.

General

Design

Alignment

Beam

Type

Dummy Member

Select Const.type Member

Accept Defaults

Press Section Button

Accept Defaults

Material = Timber

Timber

Support

Size = Sawn Softwood 50 x 100

Simple Connections

Grade = D50 E analysis = 15000 N/mm2 7] With the attribute set created ensure that the it is set as the Default attribute

set for new beams that you create. 8] Select Create and Beam.




9] Now place the dummy members at the position along the bottom of the wall

panel as shown below.

Please note that the view of the walls has been turned off using View Options for clarity. 10] Finally place walls completely around the rest of the structure spanning at

zero degrees. For a better view of walls and span directions use the wire view from the Scheme toolbar. Remember to add a wall above the flat roof area as well.

11] Validate the model.

There should be no errors or warnings.



Chapter 5

Chapter 5 : Wind Definitions for Roofs and Walls

Wind Definitions for Roofs and Walls Although you have placed both roof and wall elements into your model, there is additional information that you need to define before you can start to calculate the wind loading. We will look at this now. 1] Select the Structure view and view the structure from the North-West. 2] Activate Show / Alter State mode.

In this mode the you can see and set the details for the individual roof and wall elements in your model, by picking the appropriate option.

As you can see above you can define the inner and outer face of the walls, and the roof type.

5.1

Inner and Outer Walls We need to ensure that the correct wall is defined as the outer face of the wall. 1] Select the Wall Surface option in the Show/Alter State dialog. You should see a

display similar to that below.

When you create a wall item you must define its orientation (which is its inner and outer face) when it is subjected to wind. You can use Show/Alter State to swap the inner and outer faces of wall elements to achieve the result that you require. To do so simply click on the wall element whose orientation you want to change.




2] Rotate the structure and click any walls that have the wrong orientation to

make all the Outer faces of the wall elements face the outside of the building. When you have finished your walls should appear as shown below.

South-East Isometric View

5.2

Roof Panels Now we shall set the roof panel details for our model. 1] Select the Roof Type option in the Show/Alter State dialog. You should see a

display similar to that below.

As you can see above all the roof elements have been given the type Auto when they were defined.

5.2.1

Auto Depending on the slope of the roof element, the Auto setting will automatically set the roof to be either monopitched or flat. Generally this will yield conservative results. In many cases you may consider another type setting to be more appropriate (see clause 2.5 of BS6399-2:1997), but it is your responsibility to take control of this setting. For this Quick Start Guide example you will change four roof elements to the Duopitch setting. 1] In the Show / Alter State dialog click on the Duopitch option.




2] Change the roofs shown below from Auto to Duopitch by clicking them.


Chapter 6 : Wind Module

Chapter 6 6.1


Wind Module

BREVe Now that we have defined the roofs and walls of our model we can use the Wind Wizard to determine the wind loading. 1] Pick Loading/Wind Wizard…

You will see the BREVe2 splash screen.

Followed by the Method page of the Wind Wizard.

As you can see you have 2 options available to you for the wind code: Standard effective wind speeds with standard pressure coefficients — The standard method determines the worst case parameters for all directions around the structure in order to calculate the effective wind speed. If the orientation of the building is known, then the parameter Sd which varies depending on the wind direction will have a direct effect on the effective wind speed in that given direction. Directional effective wind speeds with standard pressure coefficients – Hybrid — If the BREVe analysis is conducted, then the directional effective wind speed is calculated for the 12 sectors around the building. For each direction the program determines the worst case wind speed over that given sector nearest to that direction.




Wind site information can be obtained from the BREVe data base or alternatively you can choose the Other option and enter the relevant wind information yourself. 2] Make the settings shown in the capture above and then click Next.

This dialog needs the site location for the structure. You can provide this information either by giving a grid reference or a selecting a position from a map. There are several Internet based tools available to you which allow you to determine the Ordnance Survey grid reference from a postcode or given location, for example www.streetmap.co.uk or www.multimap.co.uk. 3] Click Site By Ref to see the Site Selector dialog.

Note

You can either enter the Grid reference or the Easting and Northing positions in metres to define the site location.

From the information given at the start of the Quick Start Guide, the location of our structure is in Leeds with the grid reference of SE298339. 4] Enter this Grid reference into the dialog and click OK.

An alternative method for determining the wind information is to use maps and select the location from these. With the site location established BREVe will automatically create the site parameters: • Basic Wind speed

• Effective wind Speed • Ground Roughness Categories • Altitude, and so on All the default factors shown in the following calculations are safe values based on a 1 km square and based on the BREVe database. If you want to improve on this 1 km accuracy then you can enter the various parameters manually. In this case you would pick the Manually improve 1 km resolution option. For our example we will use the safe parameters within 1km square option, so ensure that this is selected.




Once the site location is established BREVe automatically establishes the altitude at that location. You can alter this either by using the Manually improve 1km resolution option or by using the site editor.

On occasion you may construct your Fastrak Building Designer model with the datum level not corresponding to the ground level. The Ground Level in Fastrak Model field allows you to set the appropriate value so that the reference heights can be calculated correctly. You do not need to define the orientation of the building for the standard method. If you choose the hybrid method, then you must define the building’s orientation

If you choose the Consider Topography option, then the wind module will use the BREVe database to determine the altitude factor in accordance with BS6399 clause 2.2.2.2.3. Otherwise the data in the database is ignored and Sa is calculated using clause 2.2.2.2.2. If you pick the Consider Obstructions option, then BREVe will recover the obstruction data from the database for selected site and determine the effective height He. If obstructions are not to be considered, then He will be taken as Hr as in clause 1.7.3.2 and no reduction is applied. 5] Ensure that the data shown below is set and then click Next>.

You will see the following dialog.

Initially Fastrak Building Designer automatically calculates the wind pressures in the 4 orthogonal directions of 0, 90, 180 and 270 degrees. To view the parameters used in the BREVe analysis you can click the Details… button. The Structure report contains details of the parameters of the BREVe analysis after the wind wizard has been completed. (Pick File/Report/Structure). 6] To complete the Wind Wizard click Finish.



6.2


Wind Vortex View The Wind Vortex view appears on completion of the BREVe analysis.

This view allows you to see the effective wind speeds approaching the building in the 12 different directions. The four individual directions that were accounted for in the BREVe wizard are shown by the black arrows (highlighted above). The view also allows you to see the change in effective wind speed at the eaves and the apex levels of the structure.

Since the orientation of the building is not required, north is not shown on the wind vortex view. As explained previously, with the topography being ignored, and with the directional factor Sd being taken as 1.0 in all directions, and no reduction influences applied for obstructions, the effective wind speeds are equal in all directions surrounding the structure. Note

6.3

To rotate the view of the structure click and drag using the right mouse button.

The Workspace Window Once the BREVe analysis has been completed the workspace window changes to show the validation of the pressure zones for the structure and individual directions which have been calculated.




Note

The Wind Loading tab at the bottom of the workspace window.

You can look at the wind vortex view at any time. Simply right click Wind Model in the Workspace and then pick Open Wind Vortex View from the context menu.

The tick next to Pressure Zones in the Workspace indicates that all the roof- and wall-elements are valid for the wind pressures in the directions which are shown. You can expand the Wind Directions information for a direction and then expand the information for the Roof Zones and Wall Zones to see the individual zones that have been defined.

6.4

Directional Pressure Coefficients For the wind directions we have defined, we can see an individual wind directional view which provides the pressure coefficients on the structure. 1] Right click on the Wind Directions entry Dir. 0.00 then pick Open Wind Direction View from the context menu.




You will see the following view.

2] Follow a similar process to open the view for Dir. 90.00.

The zones shown above reflect the roof type settings. The single sloping roof left as Auto is treated as a monopitch as its slope is more than 5 degrees. The other roof set to Auto is of course treated as flat. With these designations the external pressure coefficients were obtained from tables 8, 9 and 10 from BS6399.

6.4.1

Other Optional Information Other optional information is available using View Options.

6.5

Creating Wind Load Cases Once the BREVe analysis has been completed and the wind and wall elements are validated you can proceed to create loadcases for the individual wind directions.



6.5.1


The wind loading Icons The Wind toolbar allows you to access the Wind Wizard, update the wind zones if you make changes to your roofs or walls, and define the wind loadcases which apply to your structure. Wind Wizard

Wind Loadcase Update Zones

The Update Zones and Wind Loadcases commands are also available in the context menu obtained by right clicking in a Wind Direction view. 1] Click the Wind Loadcases icon.

You use this dialog to define the wind loadcases. 2] Click Add.

Name — Fastrak Building Designer automatically sets the name depending on the parameters which you have established. Direction — The direction for the wind for which the loadcase is being created. ae — Load sharing external diagonal dimension. +ve Cpe — The use of positive external pressure coefficient for roof zones. ai — Internal diagonal dimensions (you must set the value manually). Cai — Default internal pressure coefficient (0.3, 0.0, +0.2). Note

The only coefficient that you need to define manually is the internal diagonal loading dimension ai, but you should check all values when creating loadcases to ensure that the loadcase is as you intend.



6.5.2


Determining the Internal Loading Dimension, ai For a building which contains external windows and doors which may be kept closed and any internal doors which will be generally left open, the relevant diagonal dimension ai may be taken as, a i = 10 × 3 Internal volume

The internal volume may be taken as the whole volume of the structure, a volume of a storey height or an individual volume of a room. For our structure we will use the internal volume of the storey, thus. a i = 10 × 3 Internal volume of storey

The floor to floor height between the first and second floor is 3.5 metres. You can use the Buildings Levels command to check this. You can find the Floored area by using the Material Listings command. 1] Select Design/Material Listing… and then pick the Floored Area tab.

Therefore the volume for the first floor is given as, Storey volume = 3.5 × 836.7 = 2928.45m

2

and the internal diagonal dimension is: a i = 10 × 3 2928.45 = 143.1m

If you need to consider dominant openings then you should refer to Clause 2.6.2 of BS6399 pt-2.

6.5.3

Auto Generation of Wind Loadcases Once the internal diagonal loading dimension has been specified Fastrak Building Designer generates a range of appropriate wind loadcases automatically. 1] Delete the loadcase you previously created in the Wind Loadcases dialog. 2] Enter the value of 143.1 into the Auto ai field.




3] Click the Auto button and Fastrak Building Designer generates the following

loadcases.

For every wind direction Fastrak Building Designer generates 4 loadcases with positive and negative Cpe values and -0.3 and 0.2 Cpi values. Hence for our model which has 4 wind directions we get 16 loadcases. You can easily add more loadcases by clicking Add should you need to consider other conditions, such as a Cpi value of 0.0. 4] Click OK.

Once the loadcases are established, you can view the loads graphically either by clicking the Wind Zone Loads icon or by double clicking a loadcase in the Workspace. Wind Zone Loading icon with loadcase displayed

Wind Loadcases - double click to display

To see the wind zone loading on the structure you must be looking at a wind directional view. 5] Select the wind directional view at 0 degrees to see the view below.




6] Now double click a loadcase in the Workspace or click the Wind Load Zones icon.

The Wind Load Net Pressures are displayed as area loads on the wall and panel elements. You can use the loading drop down menu to view the 4 wind loadcases associated with this direction.

6.6

Creating Load Combinations Now to define the wind combination that we want to consider. 1] Pick Loading/Combinations… 2] Create the combination ULS+Wind @ 0degsCpi -.3, +Cpe as shown

below.

3] Now with the combination for wind established, Validate and Design the

model.




Once the analysis and design is completed the Design page of the Workspace shows the basic details for each wind loadcase as shown below.

4] Change to the Structure view and use View Options to switch on the view of the

decomposed loads. 5] Using the Loadcase toolbar pick one of the wind loadcases that you generated and the Structure window will show the loads that have been decomposed to

your structure.



Chapter 7

Chapter 7 : What Next?

What Next? In this example you have created a wind analysis for a small model, this may give you the confidence to go on and try something for yourself. However, we would suggest that you book yourself on the next available Fastrak Wind Modeller training day1, where you will find that our expert tuition gives you a flying start, ensuring that you are fully productive in the shortest possible time. You might also want to look at the online documentation or help file which contain a continuation to this worked example. This covers more of Fastrak Wind Modeller’s features than has been possible in this short document and takes the wind modelling of your example a little further.

Footnotes 1. Contact our Support Department for details.


Chapter 8 : The Wind Modeller Quick Start Guide Continues

Chapter 8 8.1


The Wind Modeller Quick Start Guide Continues

Saved files As we created this extension to the worked example we saved the model away at the start of each chapter1 and numbered these saved models according to the chapter number. Thus if you want to pick the example up at a particular point, rather than working through it in its entirety, you can simply open the appropriate file. If you want to load the example as it stands at this point (the start of chapter 8), then the file you need to open is Wind QS Example 08.fastrak, if you wanted to open the example as it stands at the start of chapter 3, then that’s in the file Wind QS Example 03.fastrak and so on. You will find these files in the \documents and settings\All Users\Documents\Fastrak\Examples folder. You can open and use these files, but you can not save them away unless you change their names, this is done to protect the originals.

8.2

Modification of Wind Loading We will now make the changes described below to our model’s wind data: • the main roof slopes will be changed from Duopitch to Hip Main,

• a new wind direction will be considered of 15 degrees, • topography and obstructions will be considered in the BREVe analysis, • we will also consider defining Wind Data when the BREVe analysis is not used.

8.3

Changing the type of a roofing panel element Previously four of the roof elements were defined as having the Duopitch type, therefore during the wind assessment the external pressure coefficients were obtained from BS6399 table 10. Sometimes it may be appropriate to consider a different roof type for one or more wind directions, but not all. In this example we will change these to have the Hip main type for the 90 degree direction only. 1] Select the Wind at 90 view and view the structure from the South-East.

Footnotes 1. Starting with chapter 3 which is where the example proper starts.

E:\CSC Doc\Building Designer\Quick Start Guide\Wind Modeller Quick Start Guide 2.fm



2] Click the Show/Alter State icon.

3] In the Show/Alter State dialogue highlight the options for roofs types and

select Hip Main. 4] Change the Roofs shown by the arrows below to Hip Main by clicking them.

If you do make changes using a directional view, then you should be aware that the changes will only take effect for that wind direction. If you want to make changes which affect the model globally, then you should use the Wind Vortex view or Structure view to achieve this. 5] Close the Show/Alter State dialog and look at the Wind tab of the Workspace .

As you can see there is a validation issue with the wind pressure zones, in particular with the zones for some of the individual roof elements. Expand the Dir 90.0000 and Roof Zones branches to see the items.

Since you changed the type of some of the roofing panels, the wind pressure zones have to be updated to accommodate the changes you have made.




6] On the Wind toolbar click Update Zones. Update Zones

The Workspace is updated to show the new status of the roof panels and graphical display for the wind direction is updated to show the new zone layout.

When you make changes in the Wind Vortex View or the Structure View, then the changes affect all the wind directions you have established. Thus when you click Update Zones, all the directions are updated and validated to accommodate your changes.

8.4

Establishing a New Direction for Wind In order to add a new direction to the wind analysis you need to run the Wind Wizard again. 1] Either pick Loading/Wind Wizard… or click the or select the Wind Wizard icon. 2] On the first dialog select the options shown below and then click Next>.

The Wind Wizard remembers the current settings, so you will find that the location of the site remains unchanged – Leeds with a grid reference of SE298339. However, this time for the wind analysis we will set the orientation of the building relative to the Fastrak Building Designer axes by defining the Orientation of North Relative to Fastrak axes to 180 degrees. We will also set the options to Consider Topography and any to Consider Obstructions. Finally we will add an extra direction to consider the wind at 15 degrees.




3] Set the options shown below and then click Next>.

In the Wind Effective Wind Speeds Directions dialog we need to add the new direction of 15 degrees. 4] Click Add Dir to add a new direction line and then enter a value of 15 in the Fastrak Directions column as shown below.

The data as shown above is invalid since the directions have to be in order. 5] Click Sort Dirs.

Note

The Sd values for the various directions are different – this affects the final magnitude of the wind force. For further information click Details…

6] Click Finish and look at the Wind Vortex View.

The Wind Vortex View shows the differing magnitudes of effective wind speeds surrounding the building, it also shows the new direction of 15 degrees, and the north direction relative to the Fastrak Building Designer axes.




7] Click the Wind Loadcase icon to define the loadcases for the new direction. You

will see that the existing loadcases are maintained. You can now enter the loadcase information for the new direction of 15 degrees manually using the Add button as described previously.

You can create combinations to include these wind loadcases in the usual manner.

8.5

Editing Individual Wind Zone Loading To obtain further information on any wind zone you can single click on that zone. 1] Pick the Wind at 0.000 deg window. In the Loading toolbar click the Wind Zone Loads icon, and from the drop list pick the Wind 0.000, Cpi 0.200, +Cpe

loadcase.

Single left click on the zone

2] Single left click the zone shown above. You will see the Wind Zone Load Data

dialog.

8.5.1

Editing Defaulted Values By removing the check against Use Default Values you can change the values for the wind zone’s coefficients, Cpi, ae and ai.




1] Remove the check against Use Default Values and change the Cpi value to 0.0.

2] Click OK and you will see the net pressure for the zone change.

6

8.6

Using the Fastrak Wind Modeller without BREVe In certain locations, for example Southern Ireland, BREVe wind analysis is not available. In such locations you must enter the site and wind information manually in order to determine the effective wind speed. We will use the following information for the wind analysis. • Location = Dublin City

8.6.1

• Altitude • Basic Wind Speed • Site Location

= 153 m above sea level

• Surrounding Shelter Height • Upwind Spacings • Ground Roughness

=7m

= 23 m/s = 10 km from the sea, = 2 km from the edge of town = 30 m = Town

Standard “Other” Method 1] Start the BREVe Wind Wizard using the menu or toolbar icon. 2] Set the Standard Effective Wind Speed Method for the Wind Code. 3] Pick Other as the Data Source. (we are NOT using the BREVe database).




4] Click Next> to see the following screen.

5] Enter the Altitude as 153 m and click Next> to see the Other Standard Wind Data page of the Wind Wizard . 6] Complete the dialog as shown below and then click Next>.

You will see the Effective Wind Speeds dialog. The Wind Vortex View will show the wind loading in the orthogonal 4 directions and the 15° direction we defined earlier. Click on the line relating to this direction and then click Del Dir..

8.6.2

The Sd Value Unless you can justify the use of a different Sd value you should leave the default value of 1.0 in all directions.

8.6.3

The Other Hybrid Method (Information Only) 1] Run the Wind Wizard . Select the Hybrid and Other options and then click Next>.




2] The previous altitude of 153m is maintained, so simply click Next>. This time you will see the Other Hybrid Wind Data page.

This page of the wizard allows you to define basic wind data which is dependent on a given direction. You can modify the parameters for each direction individually. The Effective Wind Speeds dialogue.

A possible Wind Vortex view.

Congratulations you have now finished this extension to the Quick Start Tutorial. We hope that you have found the additional features it has covered both interesting and helpful.


BS6399-2 Wind Modeller Quick Start Guide

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