ASCE7-05 Wind Wizard Handbook

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ASCE7-05&-10 WIND MODELLER

Tuesday 27 November 2012 13:30

ASCE7-05 Wind Modeller Handbook page 2

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Table of Contents

ASCE7-05&-10 Wind Modeller Handbook

Chapter 1 Introduction . . . . . . . . . . . . . . . 5

Chapter 2 Scope . . . . . . . . . . . . . . . . . 6

Chapter 3 Limitations . . . . . . . . . . . . . . . . 7

Chapter 4 Applying Walls and Roofs . . . . . . . . . . . . . 10Applying Walls . . . . . . . . . . . . . . . 10Applying Roofs . . . . . . . . . . . . . . . 10

Chapter 5 Running the Wind Wizard. . . . . . . . . . . . . 11Choice of Method . . . . . . . . . . . . . . . 11Running the Wind Wizard for ASCE/SEI 7-05 . . . . . . . . . . 12Running the Wind Wizard for ASCE/SEI 7-10 . . . . . . . . . . 17Results. . . . . . . . . . . . . . . . . 21

Chapter 6 Creating Wind Zones on the Building . . . . . . . . . . 22ASCE7-05 - Low Rise Building Method . . . . . . . . . . . 22ASCE7-05 - All Heights Method . . . . . . . . . . . . 23ASCE7-10 - Low Rise Building Method . . . . . . . . . . . 25ASCE7-10 - All Heights Method . . . . . . . . . . . . 25

Chapter 7 Creating Wind Loadcases . . . . . . . . . . . . . 28

Chapter 8 Load Decomposition . . . . . . . . . . . . . . 29Roofs . . . . . . . . . . . . . . . . . 29Walls . . . . . . . . . . . . . . . . . 29

Chapter 9 References . . . . . . . . . . . . . . . . 30

Chapter 1 : Introduction ASCE7-05&-10 Wind Wizard page 5ASCE7-05&-10 Wind Modeller Handbook

Chapter 1 Introduction

This handbook describes the ASCE7- 05&-10 Wind Modeller, a component of Fastrak Building Designer which allows you to load a model for wind in accordance with either ASCE/SEI 7-05(Ref. 1) or ASCE/SEI 7-10(Ref. 2). The wind loading assessment is performed on the walls and roofs which are defined in your building model. The resulting wind loads are distributed back to the Main Wind-Force Resisting Systems in your building during structural analysis for design.

The Wind Modeller allows you to generate these loads via a choice of methods.

If designing to ASCE 7-05 you can choose between: Method 2 - Rigid Buildings of All Heights (Clause 6.5.12.2.1) Method 2 - Low-Rise Buildings (Clause 6.5.12.2.2)

If designing to ASCE 7-10 you can choose between: Directional Procedure Part 1 - Rigid Buildings of All Heights (Chapter 27) Envelope Procedure Part 1 - Low-Rise Buildings (Chapter 28)

You can use the Wind Modeller to: Determine main wind parameters, Determine zone wind pressures on walls and roofs, Determine pressure coefficients for each zone, Determine wind pressures on each zone Determine wind loads and loadcases/ combinations for your structure.

Note The Wind Modeller will only generate loads for the design of the Main Wind-Force Resisting Systems. The resulting loads are not intended to be used for the design of individual components or cladding.

You will find that the determination of the pressures and the zones is rigorous but the final wind loads adopted are your responsibility.

If necessary you can override the calculated parameters, zoning and load information to take account of more accurate information you may possess.

The Wind Modeller is a very flexible tool that can, should you wish, be used purely for wind assessment by setting up a model of consisting only of walls and roofs (no members) you can then determine the wind loading on the building envelope.

Unless explicitly noted otherwise, all clauses, figures and tables referred to in this document are from the ASCE 7-05(Ref. 1) and ASCE 7-10(Ref. 2) as appropriate.

ASCE7-05&-10 Wind Wizard page 6 Chapter 2 : ScopeChapter 2 Scope

The ASCE7- 05&-10 Wind Modeller should be used on a Fastrak Building Designer model which has previously been clothed in walls (i.e. wind walls, not shear walls) and roofs. For the building to be valid connected walls must have consistent normal directions. The onus is on you to model the building shape as completely and as accurately as you determine necessary.

Wind is applied intelligently to this building envelope within the scope below and the limitations clearly laid out in the next section.

It is assumed that the wind loads are developed to assess the overall stability of the structure and for member design. The wind loads have not been specifically developed for the design of cladding and fixings.

The scope of the Wind Modeller encompasses: Choice of method:

ASCE/SEI 7-05 - Method 2 - Rigid Buildings of All Heights ASCE/SEI 7-05 - Method 2 - Low-Rise Buildings ASCE/SEI 7-10 - Directional Procedure Part 1 - Rigid Buildings of All Heights ASCE/SEI 7-10 - Envelope Procedure Part 1 - Low-Rise Buildings

The input of appropriate basic wind data is your responsibility. Having defined walls and roofs (defaults are standard wall, flat or pitched roof depending

on the slope), you are able to specify the type in more detail e.g. monoslope / mansard etc. Wherever possible the wind parameters are determined for you but conservatively, you are

able to override the values should you wish to. Given the above, zoning is semi-automatic, with full graphical feedback. Provision is made

for you to modify the zoning. For example you can define a manual zone layout, you can override the coefficients

Load decomposition is fully automatic where valid, (walls and roofs need to be fully supported in the direction of span). Please note that the decomposition for walls results in nodal loads rather than distributed loads.

There may be situations when you perceive a need to manually define loads that can not be determined automatically. You can do this by defining additional wind load cases to contain these loads and then include these with the relevant system generated loads in design combinations in the normal way.

Chapter 3 : Limitations ASCE7-05&-10 Wind Wizard page 7Chapter 3 Limitations

Throughout the development of the ASCE7- 05&-10 Wind Modeller extensive reference has been made to the standards (Ref. 1), (Ref. 2) and we consider it advisable that you are fully familiar with these before using the software.

In addition, because wind loading is complex and its application to general structures even more so, it is essential that you read and fully appreciate the following limitations in the software:

The shape of the building must lie within the shapes that are valid according to ASCE7-05 Clause 6.5.1, or ASCE7-10 Clauses 27.1.2 and 28.1.2:

It should be a regular shaped building or structure It should not have response characteristics making it subject to across-wind loading,

vortex shedding, instability due to galloping or flutter; or have a site location for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration.

Although the software will generate wind loads for many situations - it is up to you to accept that the loads generated are suitable according to ASCE7-05&-10.

Other documented limitations include: Buildings must be enclosed or partially enclosed Open sided buildings are not considered. Only rigid buildings are considered, not flexible buildings. Zones and load cases are not generated for components and cladding. You will need to establish and enter the wind data yourself. Roof types must be set manually. Exposed members are not considered, for example lattices, trusses Barrel-vault and domed roofs are not considered. Parapets and free-standing canopies are not considered. Roof Overhangs are not explicitly handled. The design wind load is not explicitly checked to ensure it is greater than the minimum of:

ASCE 7-05 = 10 psf - (as per Clause 6.1.4.1.) ASCE 7-10 = 16 psf - (as per Clause 27.4.7 for the Directional method, or 28.4.4 for the

Envelope procedure.) However, the average wind pressure for each of Windward, Leeward and Side directions is provided for you to manually check this is satisfied.

There is no special handling for Multi-Bay roofs as they are not covered explicitly in ASCE 7-05 or ASCE 7-10.

There is no special handling for troughed roofs as they are not covered explicitly in ASCE 7-05 or ASCE 7-10.

Load decomposition onto shear walls

ASCE7-05&-10 Wind Wizard page 8 Chapter 3 : Limitations All wall loads are decomposed into nodal loads. In a building that contains a shear wall, the analytical model of the shear wall consists partly of a mid-pier vertical column at the center of the shear wall, hence wind wall loads will be decomposed onto the mid-pier column.

This decomposition on to the mid pier column could in certain cases result in an averaging of the wind pressure profile that removes the localized pressure increase at the corners of the building.

The example below illustrates the problem and provides an alternative model as a workaround:

Physical model of shear wall

Although not shown here, wind walls are also added to all four faces of the building.

Wind zones

The zones are generated on the wind wall faces.

Resulting stepped wind pressure on wind wall faces

Highest pressure occurs in Zone A, lesser pressure exists in other zones

Chapter 3 : Limitations ASCE7-05&-10 Wind Wizard page 9Wind pressure decomposed on to the shear wall

Stepped pressure gradient is averaged over the face of the shear wall and then decomposed on to the mid-pier column at its center. Hence only a single point load is applied at each floor level.

Alternative Model

Define two adjacent shear walls, making the first as wide as wind zone A. This results in a more accurate decomposition of the wind load, reflecting the stepped profile of the wind pressure.

ASCE7-05&-10 Wind Wizard page 10 Chapter 4 : Applying Walls and RoofsChapter 4 Applying Walls and Roofs

All the calculations for wind depend on the geometry and inter-connectivity of the walls and roofs that envelope the building. You must therefore define the model, together with its walls and roofs before you can start to calculate the wind loading using the Wind Modeller.

Whilst defining the models walls and roofs, it is essential that you define the largest planar surfaces possible for these if you want to get the best results. If you ignore this advice, then the calculation of the reference height can be unconservative.

Applying Walls A single wall is determined to be a single planar surface. The outward face is vitally important for determining the wind direction relative to the wall, that is windward or leeward.

It is recommended that you use Wind Modellers Show/Alter State (Building/Wall Surface) feature to check the face orientation quickly and correct any mistakes by clicking once on an item to reverse the direction. However, whenever automatic zoning is carried out, for example at the end of the Wind Wizard, the connected walls are checked to ensure that the normal directions are not inconsistent.

Applying Roofs A single roof is determined to be a single planar surface. The orientation of a roof is automatically determined when placed based upon the slope vector the line of maximum roof slope.

The default roof type depends on the slope. If the slope is zero it is flat, otherwise it is pitched. It is the users responsibility to alter the type using Show/Alter State as required.

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 11Chapter 5 Running the Wind Wizard

Once the walls and roofs are in place, you use the Wind Wizard to define sufficient site information to calculate the velocity pressures for the required wind directions and heights around the building.

Choice of Method If designing to ASCE/SEI 7-05 you can choose between:

Method 2 - Rigid Buildings of All Heights (Clause 6.5.12.2.1) Method 2 - Low-Rise Buildings (Clause 6.5.12.2.2)

If designing to ASCE/SEI 7-10 you can choose between: Directional Procedure Part 1 - Rigid Buildings of All Heights (Chapter 27) Envelope Procedure Part 1 - Low-Rise Buildings (Chapter 28)

Applicability of the Low-Rise Building methodThe Low-Rise Building method is explicitly limited to buildings where the mean roof height does not exceed the least horizontal dimension and is less than or equal to 60 ft, (ASCE7-05 Clause 6.2 and ASCE7-10 Clause 26.2). It is implied that the method should only be used for simple rectangular box-shaped buildings, however, you are given the final responsibility for determining the applicability of this method to your model.

Failure to comply with any of the following conditions will explicitly prevent access to this method:

There must be 4 walls which must be connected sequentially and form a simple quadrilateral in plan form, (all internal corners between 82.5 and 97.5).

Each wall must be almost vertical (>80) Each wall must either have 4 sides, forming a simple quadrilateral in elevation, or 5 sides

forming a convex shape, (allowing for gable ends of buildings). The roof system must be one of the following:-

Single quadrilateral roof with type Flat

Note Where a building has a single roof with a low slope, (e.g. 2), the default will be Pitched, but if you consider the building suitable for the Low-Rise method, you can force the roof type to Flat rather than Monoslope

ASCE7-05&-10 Wind Wizard page 12 Chapter 5 : Running the Wind Wizard Two quadrilateral Pitched roofs which must have a single edge in common. The roofs must face in opposite directions and have similar slopes, (less than 3 difference).

Two quadrilateral Hip Main roofs which must have a single edge in common and either 1 or 2 hip gable roofs which must be triangular. The Hip Main roofs must face in opposite directions and have similar slopes, (less than 3 difference).

In particular, the Low-Rise Method is not allowed with Monoslope or multi-span roofs.

Running the Wind Wizard for ASCE/SEI 7-05

Low Rise Buildings - Geometry The following geometry items are required for the Low Rise Buildings method. You can override calculated dimensions using your engineering judgement.

Ground Level in Fastrak Model If for some reason, the level 0.0 feet in the Fastrak Building Designer model does not correspond to the ground level, e.g. you have used a site datum rather than a building datum, then this field allows you to set the appropriate value so that the reference heights for the wind can be calculated correctly. The default is zero. The allowed maximum is the minimum wall or roof height. Changing the value in this field will cause the Mean Roof Height to be recalculated, unless you have chosen to override that dimension.

Orientation of Longitudinal Direction relative to Fastrak axes (Figure 6-10) This information is required to control the orientation of the Transverse and Longitudinal directions, and thus the Fastrak Wind Directions. For simple roof shapes the Wind Wizard will calculate a default value as below.

Single flat roof - orient along longest side, 2 Duopitch roofs - orient along common edge, 2 Hip Main roofs - orient along common edge.

Changing the value in this field will cause either or both of the Longitudinal and Transverse Dimensions to be recalculated, unless you have chosen to override them.

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 13To help you understand the orientation, a 3D Wind Vortex view is automatically created. This is updated at each stage of the Wind Wizard and illustrates the orientation of the building, wind directions and the velocity pressures.

Roof Angle The field is always visible, even if there are no roof items in your model. It is calculated as follows:

No roof items - = 0. Else - use maximum angle for all roofs in the model.

You are able to override the calculated value by checking the box; The limits are 0 to 80.

Mean Roof Height, h (Clause 6.2) The field is calculated as follows: No roof items -h is maximum reference height for walls, Else if

ASCE7-05&-10 Wind Wizard page 14 Chapter 5 : Running the Wind WizardRigid Buildings of All Heights - Geometry The following geometry items are required for this method. You can override calculated dimensions using your engineering judgement.

Ground Level in Fastrak Model If for some reason, the level 0.0 feet in the Fastrak Building Designer model does not correspond to the ground level, for example you have used a site datum rather than a building datum, then this field allows you to set the appropriate value so that the reference heights for the wind can be calculated correctly. The default is zero. The allowed maximum is the minimum wall or roof height. Changing the value in this field will cause the Mean Roof Height to be recalculated, unless you have chosen to override that dimension.

Orientation of Principal Axes relative to Fastrak axes This is similar to the Orientation of Longitudinal Direction relative to Fastrak axes (Figure 6-10) for Low-Rise Buildings. Although there is no need to distinguish between the Longitudinal and Transverse axes for this method, the wind X axis will be aligned to this direction with the Y axis at right angles. The vortex view will be slightly different to the Low-Rise one to reflect that.

Due to the potential complexity of the model, ASCE7- 05 Wind Wizard will only attempt to determine the correct angle for the axes if the building is also suitable for Low Rise, otherwise zero is used as the default.

Mean Roof Height (h) (Clause 6.2) For this method, the actual reference height is only be used for the pressure on windward walls. For all other walls, and roofs, a single height is used to determine the pressure for each direction.

By default, the height is calculated as for Low-Rise Buildings except that there is no single value of , so the eaves height is only used if all the roof angles are

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 15For X Axis, L = X Dimension, B = Y Dimension.

For Y Axis, L = Y Dimension, B = X Dimension

Design Pressure Factor (Figure 6.9 and Clause 6.5.12.3) This defaults to 75%, but the commentary suggests that this may not cover all cases so you are allowed to change it. A single factor is used for all Torsional loadcases.

Eccentricity (Figure 6.9 and Clause 6.5.12.3) This defaults to 15% but again, the commentary suggests that this may not cover all cases so you are allowed to change it. A single factor is used for all Torsional loadcases.

Basic Wind DataOnce the geometry has been confirmed, (for either method), you are then required to enter the basic wind data. The only difference between the two methods is that the Gust Effect Factor field is only shown for the All Heights Method.

Basic Wind Speed (Clause 6.5.4) A strictly positive value is required with 90mph being the default.

Occupancy Category (Table 1-1) Options I to IV with default being II.

Hurricane-Prone Region (Clause 6.2) The default is unchecked, i.e. region not prone to hurricanes.

Directionality Factor, Kd (Clause 6.5.4.4, and Table 6-4) The default is 0.85, range 0.85 to 1.0 inclusive.

ASCE7-05&-10 Wind Wizard page 16 Chapter 5 : Running the Wind WizardNote There is no cross-checking to ensure that the model has met the load combination criteria. If that does not apply, then it is your own responsibility to enter the correct value of 1.0.

Enclosure Classification (Clause 6.5.9) Options are Enclosed and Partially Enclosed with default being Enclosed.

Note Open structures are not handled in the current version of the program.

Gust Effect Factor (Clause 6.5.8) This will only be shown for the All Heights Method. The default value is 0.85.

Principal Axes There are always four directions shown for principal axes, being based on the Orientation of the Longitudinal Direction or Principal Axes depending on the method. You are not able to add, delete or modify any direction.

Exposure Category (Clause 6.5.6.3) Options are B, C or D with default being B.

Topographic Feature (Clause 6.5.7 and Figure 6-4) Options are as follows, with the default being None:

None - no feature, i.e. Kzt = 1.0. 2D Ridge 2D Escarp - 2D Escarpment 3D Hill - 3D Axisymmetrical Hill

Crest Height, H (Figure 6-4) Height of the hill or escarpment relative to the upwind terrain.

The behaviour of this field depends on the Feature type as follows: 2D Ridge - non-zero values allowed, (negative indicates a valley). 2D Escarp - strictly positive values allowed 3D Hill - strictly positive values allowed

Crest Length, Lh (Figure 6-4) Distance upwind of crest to where the difference in ground elevation is half the height of the hill or escarpment.

Distance to Crest, x (Figure 6-4) Distance upwind or downwind from the crest to the building site.

The value may be positive to indicate downwind, or negative to indicate upwind.

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 17Running the Wind Wizard for ASCE/SEI 7-10

Low Rise Buildings - Geometry The following geometry items are required for the Low Rise Buildings method. You can override calculated dimensions using your engineering judgement.

Ground Level in Fastrak Model If for some reason, the level 0.0 feet in the Fastrak Building Designer model does not correspond to the ground level, e.g. you have used a site datum rather than a building datum, then this field allows you to set the appropriate value so that the reference heights for the wind can be calculated correctly. The default is zero. The allowed maximum is the minimum wall or roof height. Changing the value in this field will cause the Mean Roof Height to be recalculated, unless you have chosen to override that dimension.

Orientation of Longitudinal Direction relative to Fastrak axes (Figure 28.4-1) This information is required to control the orientation of the Transverse and Longitudinal directions, and thus the Fastrak Wind Directions. For simple roof shapes, ASCE7- 10 Wind Wizard will calculate a default value as below.

Single flat roof - orient along longest side, 2 Duopitch roofs - orient along common edge, 2 Hip Main roofs - orient along common edge.

Changing the value in this field will cause either or both of the Longitudinal and Transverse Dimensions to be recalculated, unless you have chosen to override them.

To help you understand the orientation, a 3D Wind Vortex view is automatically created. This is updated at each stage of the Wind Wizard and illustrates the orientation of the building, wind directions and the velocity pressures.

Roof Angle The field is always visible, even if there are no roof items in your model. It is calculated as follows:

No roof items - = 0. Else - use maximum angle for all roofs in the model.

You are able to override the calculated value by checking the box; The limits are 0 to 80.

Mean Roof Height, h (Clause 26.2) The field is calculated as follows: No roof items -h is maximum reference height for walls, Else if

ASCE7-05&-10 Wind Wizard page 18 Chapter 5 : Running the Wind WizardIn the example below, h = (hu + hl)/2 - g

h is limited to a maximum of 60 ft or the Least Horizontal Dimension, whichever is lower. You are able to override the calculated value by checking the box.

Longitudinal and Transverse Dimensions (Clause 26.3 and Figure 28.4-1) These are similar to the Overall Building X Dimension and Overall Building Y Dimension (Clause 6.3) for the Rigid Buildings of All Heights Method.

These dimensions are calculated from the smallest enclosing rectangle (considered over all roof and walls only), relative to the given orientation of the Longitudinal Direction - see figureon page 14. You are able to override each calculated value by checking its box. These values will then be used to derive the L and B dimensions for each wind direction.

For Longitudinal Wind Directions, L = Longitudinal Dimension, B = Transverse Dimension.

For Transverse directions, L = Transverse Dimension, B = Longitudinal Dimension.

Rigid Buildings of All Heights - Geometry The following geometry items are required for this method. You can override calculated dimensions using your engineering judgement.

Ground Level in Fastrak Model If for some reason, the level 0.0 feet in the Fastrak Building Designer model does not correspond to the ground level, for example you have used a site datum rather than a building datum, then this field allows you to set the appropriate value so that the reference heights for the wind can be calculated correctly. The default is zero. The allowed maximum is the minimum wall or roof height. Changing the value in this field will cause the Mean Roof Height to be recalculated, unless you have chosen to override that dimension.

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 19Orientation of Principal Axes relative to Fastrak axes This is similar to the Orientation of Longitudinal Direction relative to Fastrak axes (Figure 6-10) for Low-Rise Buildings. Although there is no need to distinguish between the Longitudinal and Transverse axes for this method, the wind X axis will be aligned to this direction with the Y axis at right angles. The vortex view will be slightly different to the Low-Rise one to reflect that.

Due to the potential complexity of the model, the Wind Wizard will only attempt to determine the correct angle for the axes if the building is also suitable for Low Rise, otherwise zero is used as the default.

Mean Roof Height (h) (Clause 26.2) For this method, the actual reference height is only be used for the pressure on windward walls. For all other walls, and roofs, a single height is used to determine the pressure for each direction.

By default, the height is calculated as for Low-Rise Buildings except that there is no single value of , so the eaves height is only used if all the roof angles are

ASCE7-05&-10 Wind Wizard page 20 Chapter 5 : Running the Wind WizardFor X Axis, L = X Dimension, B = Y Dimension.

For Y Axis, L = Y Dimension, B = X Dimension

Design Pressure Factor (Figure 27.4.8 and Clause 27.4.6) This defaults to 75%, but the commentary suggests that this may not cover all cases so you are allowed to change it. A single factor is used for all Torsional loadcases.

Eccentricity (Figure 27.4.8 and Clause 27.4.6) This defaults to 15% but again, the commentary suggests that this may not cover all cases so you are allowed to change it. A single factor is used for all Torsional loadcases.

Basic Wind DataOnce the geometry has been confirmed, (for either method), you are then required to enter the basic wind data. The only difference between the two methods is that the Gust Effect Factor field is only shown for the All Heights Method.

Basic Wind Speed (Clause 26.5.1) A strictly positive value is required with 90mph being the default.

Hurricane-Prone Region (Clause 26.2) The default is unchecked, i.e. region not prone to hurricanes.

Directionality Factor, Kd (Clause 26.6, and Table 26.6-1) The default is 0.85, range 0.85 to 1.0 inclusive.

Note There is no cross-checking to ensure that the model has met the load combination criteria. If that does not apply, then it is your own responsibility to enter the correct value of 1.0.

Chapter 5 : Running the Wind Wizard ASCE7-05&-10 Wind Wizard page 21Enclosure Classification (Clause 26.10) Options are Enclosed and Partially Enclosed with default being Enclosed.

Note Open structures are not handled in the current version of the program.

Gust Effect Factor (Clause 26.9.1) This will only be shown for the All Heights Method. The default value is 0.85.

Principal Axes There are always four directions shown for principal axes, being based on the Orientation of the Longitudinal Direction or Principal Axes depending on the method. You are not able to add, delete or modify any direction.

Exposure Category (Clause 26.7.3) Options are B, C or D with default being B.

Topographic Feature (Clause 26.8 and Figure 26.8-1) Options are as follows, with the default being None:

None - no feature, i.e. Kzt = 1.0. 2D Ridge 2D Escarp - 2D Escarpment 3D Hill - 3D Axisymmetrical Hill

Crest Height, H (Figure 26.8-1) Height of the hill or escarpment relative to the upwind terrain.

The behaviour of this field depends on the Feature type as follows: 2D Ridge - non-zero values allowed, (negative indicates a valley). 2D Escarp - strictly positive values allowed 3D Hill - strictly positive values allowed

Crest Length, Lh (Figure 26.8-1) Distance upwind of crest to where the difference in ground elevation is half the height of the hill or escarpment.

Distance to Crest, x (Figure 26.8-1) Distance upwind or downwind from the crest to the building site.

The value may be positive to indicate downwind, or negative to indicate upwind.

Results

The final page of the Wind Wizard is a summary of the velocity pressure results for the principal axes. You are able to use the Details... button to obtain additional information, including the values of intermediate factors used in the calculations.

ASCE7-05&-10 Wind Wizard page 22 Chapter 6 : Creating Wind Zones on the BuildingChapter 6 Creating Wind Zones on the Building

At the end of the Wind Wizard, the system creates default zones for all the walls and roof items for each of the defined wind directions.

Whenever this process occurs, any error and/or warning messages are written to the Output window. Where appropriate, double clicking on a message highlights the item, (although if the problem is direction specific, then you may have to switch to the relevant view).

ASCE7-05 - Low Rise Building Method

DirectionsEight zone directions evenly spaced at 45 degree intervals about the longitudinal direction are defined as follows:

Long A - (longitudinal direction + 22.5, uses data for +X' principal axis) Trans A - (longitudinal direction + 67.5, uses data for +Y' principal axis) Trans D - (longitudinal direction + 112.5, uses data for +Y' principal axis) Long D - (longitudinal direction + 157.5, uses data for -X' principal axis) Long C - (longitudinal direction + 202.5, uses data for -X' principal axis) Trans C - (longitudinal direction + 247.5, uses data for -Y' principal axis) Trans B - (longitudinal direction + 292.5, uses data for -Y' principal axis) Long B - (longitudinal direction + 337.5, uses data for +X' principal axis)

These enable the modelling of two sets of zones per principal axis with the correct reference corner in each case.

Wall Zones The Wind Wizard automatically generates wall zones, where possible, for each Direction of MWFRS Being Designed and Reference Corner in accordance with Figure 6-10.

Roof Zones The Wind Wizard automatically generates roof zones, where possible, for each Direction of MWFRS Being Designed and Reference Corner in accordance with Figure 6-10.

For flat roofs and for MWFRS parallel to the ridge line we assume Note 8 is not applicable.

Where Note 7 applies, we assume the dimension to the zone 2/3 boundary is measured horizontally.

Automatic Zoning Automatic zoning only applies to all triangular roof items and quadrilateral roof items that are not concave, that is that all of the internal angles < 180.

Chapter 6 : Creating Wind Zones on the Building ASCE7-05&-10 Wind Wizard page 23ASCE7-05 - All Heights Method

DirectionsEight zone directions evenly spaced at 45 degree intervals starting from the longitudinal direction are defined as follows:

+X - (longitudinal direction, uses qz for 1st principal axis) +X+Y - (longitudinal direction + 45, uses qz for 1st and 2nd principal axes) +Y - (longitudinal direction + 90, uses qz for 2nd principal axis) -X+Y - (longitudinal direction + 135, uses qz for 2nd and 3rd principal axes) -X - (longitudinal direction + 180, uses qz for 3rd principal axis) -X-Y - (longitudinal direction + 225, uses qz for 3rd and 4th principal axes) -Y - (longitudinal direction + 270, uses qz for 4th principal axis) +X-Y - (longitudinal direction + 315, uses qz for 1st principal axis)

The 4 directions +X,+Y,-X,-Y enable the modelling of design wind load cases 1 and 2 from Figure 6-9. The 4 intermediate directions +X+Y etc. enable the modelling of load cases 3 and 4.

Wall Zones The Wind Wizard automatically generates wall zones, where possible, in accordance with Figure 6-6.

Windward Walls are split horizontally over intermediate heights. Zones are labelled with a 'W' followed by the height at top of zone rounded to nearest foot (or meter if using metric units). Each zone uses the same Cp, (0.8 from Wall Cp table in Figure 6-6), but a different velocity pressure, qz, z being determined at the top of the zone.

Complex wall shapes are dealt with by splitting zones intelligently as illustrated below:

Leeward walls have a single zone, L, using a Wall Cp from the table in Figure 6-6, with interpolation for L/B. The velocity pressure, qh is used for all such zones.

ASCE7-05&-10 Wind Wizard page 24 Chapter 6 : Creating Wind Zones on the BuildingSide walls have a single zone, S, using the same Cp, (-0.7 from the Wall Cp table in Figure 6-6). A single velocity pressure, qh is used for all such zones.

Skew WallsThere is no guidance in ASCE7-05 for walls not orthogonal to the principal axes. However, the Wind Wizard will apply zones in those cases and it is your responsibility to check the wind loads adopted.

Roof Zones The Wind Wizard automatically generates Windward and Leeward roof zones (W and L respectively, where possible, in accordance with Figure 6-6. This is possible for Windward and Leeward roof items with >= 10, because there is only one zone. However, for < 10 and Side roof items, automatic zoning will not be carried out for all cases.

Negative and positive values of Cp are determined for each zone from the Roof Cp table in Figure 6-6.

For non-principal axis directions, it is assumed that roof loads are not required and so special zones are created, named Zero. Such zones will result in zero loading on the relevant roof items. However, if the you choose to do so you can change these to non-standard zones and enter coefficients to force loads to be applied.

When calculating the area reduction factor we use the slope area not the plan area.

Mansard roofs are not automatically detected, i.e. it is your responsibility to set the Roof Type using Show/Alter State or Properties for the model. Generally, Mansard roofs are handled exactly the same as if they are:

Flat (for slope < 0.1) Pitched (for slope >= 0.1)

There is no guidance on what to do with other multipitch roofs, so they are treated as pitched roofs, whether they have been flagged as Mansard or not.

Side roofs are split into to 4 zones depending on the size of the roof. See the Roof Cp table in Figure 6-6.

Zone 1 - 0 to h/2, interpolating between 2 values for h/L if necessary.

Note Upper value for interpolation can be reduced linearly with the sloped area of this zone, (see ** in Figure 6-6).

Zone 2 - h/2 to h, interpolate between -0.9 and -0.7 for h/L if necessary Zone 3 - h to 2h, interpolate between -0.5 and -0.7 for h/L if necessary Zone 4 - > 2h, interpolate between -0.3 and -0.7 for h/L if necessary

Automatic Zoning Automatic zoning will apply to all Windward and Leeward roof items with > 10, because there is only one zone. However, for < 10 and Side roof items, automatic zoning will not be carried out for all cases.

Chapter 6 : Creating Wind Zones on the Building ASCE7-05&-10 Wind Wizard page 25ASCE7-10 - Low Rise Building Method

DirectionsEight zone directions evenly spaced at 45 degree intervals about the longitudinal direction are defined as follows:

Long (B) 1 - (longitudinal direction + 22.5, uses data for +X' principal axis) Trans (A) 1 - (longitudinal direction + 67.5, uses data for +Y' principal axis) Trans (A) 1 - (longitudinal direction + 112.5, uses data for +Y' principal axis) Long (B) 4 - (longitudinal direction + 157.5, uses data for -X' principal axis) Long (B) 3 - (longitudinal direction + 202.5, uses data for -X' principal axis) Trans (A) 3 - (longitudinal direction + 247.5, uses data for -Y' principal axis) Trans (A) 2 - (longitudinal direction + 292.5, uses data for -Y' principal axis) Long (B) 2 - (longitudinal direction + 337.5, uses data for +X' principal axis)

These enable the modelling of two sets of zones per principal axis with the correct reference corner in each case.

Wall Zones The Wind Wizard automatically generates wall zones, where possible, for each Direction of MWFRS Being Designed and Reference Corner in accordance with Figure 28.4-1.

Roof Zones The Wind Wizard automatically generates roof zones, where possible, for each Direction of MWFRS Being Designed and Reference Corner in accordance with Figure 28.4-1.

For flat roofs and for MWFRS parallel to the ridge line we assume Note 8 is not applicable.

Where Note 7 applies, we assume the dimension to the zone 2/3 boundary is measured horizontally.

Automatic Zoning Automatic zoning only applies to all triangular roof items and quadrilateral roof items that are not concave, that is that all of the internal angles < 180.

ASCE7-10 - All Heights Method

DirectionsEight zone directions evenly spaced at 45 degree intervals starting from the longitudinal direction are defined as follows:

+X - (longitudinal direction, uses qz for 1st principal axis) +X+Y - (longitudinal direction + 45, uses qz for 1st and 2nd principal axes) +Y - (longitudinal direction + 90, uses qz for 2nd principal axis)

ASCE7-05&-10 Wind Wizard page 26 Chapter 6 : Creating Wind Zones on the Building -X+Y - (longitudinal direction + 135, uses qz for 2nd and 3rd principal axes) -X - (longitudinal direction + 180, uses qz for 3rd principal axis) -X-Y - (longitudinal direction + 225, uses qz for 3rd and 4th principal axes) -Y - (longitudinal direction + 270, uses qz for 4th principal axis) +X-Y - (longitudinal direction + 315, uses qz for 1st principal axis)

The 4 directions +X,+Y,-X,-Y enable the modelling of design wind load cases 1 and 2 from Figure 27.4-8. The 4 intermediate directions +X+Y etc. enable the modelling of load cases 3 and 4.

Wall Zones The Wind Wizard automatically generates wall zones, where possible, in accordance with Figure 27.4-1.

Windward Walls are split horizontally over intermediate heights. Zones are labelled with a 'W' followed by the height at top of zone rounded to nearest foot (or meter if using metric units). Each zone uses the same Cp, (0.8 from Wall Cp table in Figure 27.4-1), but a different velocity pressure, qz, z being determined at the top of the zone.

Complex wall shapes are dealt with by splitting zones intelligently as illustrated below:

Leeward walls have a single zone, L, using a Wall Cp from the table in Figure 27.4-1, with interpolation for L/B. The velocity pressure, qh is used for all such zones.

Side walls have a single zone, S, using the same Cp, (-0.7 from the Wall Cp table in Figure 27.4-1). A single velocity pressure, qh is used for all such zones.

Skew WallsThere is no guidance in ASCE7-10 for walls not orthogonal to the principal axes. However, the Wind Wizard will apply zones in those cases and it is your responsibility to check the wind loads adopted.

Chapter 6 : Creating Wind Zones on the Building ASCE7-05&-10 Wind Wizard page 27Roof Zones The Wind Wizard automatically generates Windward and Leeward roof zones (W and L respectively, where possible, in accordance with Figure 27.4-1. This is possible for Windward and Leeward roof items with >= 10, because there is only one zone. However, for < 10 and Side roof items, automatic zoning will not be carried out for all cases.

Negative and positive values of Cp are determined for each zone from the Roof Cp table in Figure 27.4-1.

For non-principal axis directions, it is assumed that roof loads are not required and so special zones are created, named Zero. Such zones will result in zero loading on the relevant roof items. However, if the you choose to do so you can change these to non-standard zones and enter coefficients to force loads to be applied.

When calculating the area reduction factor we use the slope area not the plan area.

Mansard roofs are not automatically detected, i.e. it is your responsibility to set the Roof Type using Show/Alter State or Properties for the model. Generally, Mansard roofs are handled exactly the same as if they are:

Flat (for slope < 0.1) Pitched (for slope >= 0.1)

There is no guidance on what to do with other multipitch roofs, so they are treated as pitched roofs, whether they have been flagged as Mansard or not.

Side roofs are split into to 4 zones depending on the size of the roof. See the Roof Cp table in Figure 27.4-1.

Zone 1 - 0 to h/2, interpolating between 2 values for h/L if necessary.

Note Upper value for interpolation can be reduced linearly with the sloped area of this zone, (see ** in Figure 27.4-1).

Zone 2 - h/2 to h, interpolate between -0.9 and -0.7 for h/L if necessary Zone 3 - h to 2h, interpolate between -0.5 and -0.7 for h/L if necessary Zone 4 - > 2h, interpolate between -0.3 and -0.7 for h/L if necessary

Automatic Zoning Automatic zoning will apply to all Windward and Leeward roof items with > 10, because there is only one zone. However, for < 10 and Side roof items, automatic zoning will not be carried out for all cases.

ASCE7-05&-10 Wind Wizard page 28 Chapter 7 : Creating Wind LoadcasesChapter 7 Creating Wind Loadcases

It is not practical to automatically determine critical combinations and thus required wind loadcases. Therefore you control the generation of appropriate Wind Loadcases manually. This achieved via the Wind Loadcases dialog (accessed via the Workspace or the toolbar button).

You specify which direction the loadcase will be created for and set default values for all the zone loads generated in the loadcase.

Within the Wind Loadcases dialog is an button. this provides various options to control the number of loadcases generated.

The loads can be viewed graphically either by double clicking on a wind loadcase in the Workspace, or by using the Wind Zone Loads button in the Loadcase toolbar.

Once generated these loadcases are standard Fastrak load cases so you can include them in combinations in the normal manner.

Try to use engineering judgement to identify the critical loadcases so that the number of load combinations that need to be considered can be minimized.

Torsional LoadcasesWhen generating a wind loadcase you are able to flag if it is a Torsional Loadcase or not.

When creating the torsional loadcases, reduced pressure loads are applied to parts of the standard zones (by applying a net pressure factor of 25%).

All Heights Method - Design Wind load Cases (ASCE7-05 Figure 6-9 & ASCE7-10 Figure 26.8-1)We have assumed that side wall and roof loads should be applied for Case 1. Thus by default these are included for our standard load cases for the 4 principal axes, for example, Wind+X,GCpi-0.55,-Cpi. In order to allow for Note 9 of ASCE7-05 Figure 6-6 (or ASCE7-10 Figure 27.4-1), the button can be used to create an additional load case which ignores roof loads, e.g. Wind +X,GCpi -0.55.

We have further assumed that side wall loads are included for Case 2 but roof loads are not. Case 2 is handled by the torsional case for the 4 principal axes, e.g. Wind +X,GCpi -0.55,-MT. You can add the roof loads to such cases if you wish.

We do not define actual roof zones for the intermediate wind directions because they are excluded from Cases 3 and 4. However, it is possible to define your own zone data and so add roof loads to those Cases.

Wind Loadcases

Chapter 8 : Load Decomposition ASCE7-05&-10 Wind Wizard page 29Chapter 8 Load Decomposition

Roofs The direction of the one way decomposition of the wind zone loads to roof members is as specified by the span direction of the roof. All types of elements (except bracing and cold rolled members) are considered during the load decomposition.

Walls Wall load decomposition depends on the setting of the Load on Member wall attribute:

The default setting for this attribute is No and results in nodal loads on the supporting members. This setting is generally appropriate to avoid lateral loads on simple beams and distributed loads on simple columns.

Setting Load on Member to Yes allows the generation of uniform distributed loads on portal stanchions and gable posts without the need to model side rails.

Irrespective of the setting of this attribute, the initial decomposition of wind zone loads to wall members is similar to the roof decomposition. Again all types of elements are considered except bracing and cold rolled members.

If Load on Member is set to No a second decomposition stage is undertaken: Full/partial uniform and varying distributed loads on elements (lengths of beams/columns

between nodes) are distributed back to nodes as if the elements were simply supported at either end.

The final nodal load is the sum of all incoming element loads.

Note This second stage is always performed if the members supporting the wall are simple columns or shear walls, irrespective of the Load on Member setting.

ASCE7-05&-10 Wind Wizard page 30 Chapter 9 : ReferencesChapter 9 References

1. ASCE/SEI 7-05. Minimum Design Loads for Buildings and Other Structures. ASCE, 2006. ISBN: 0-7844-0809-2.

2. ASCE/SEI 7-10. Minimum Design Loads for Buildings and Other Structures. ASCE, 2010. ISBN: 978-0-7844-1085-1.

3. Kishor C. Mehta and James M. Delahay (2004). Guide to the Use of the Wind Load Provisions of ASCE 7-02. ASCE Press. ISBN: 0-7844-0703-7.

ASCE7-05 Wind Wizard HandbookChapter 1 IntroductionChapter 2 ScopeChapter 3 LimitationsChapter 4 Applying Walls and RoofsApplying WallsApplying Roofs

Chapter 5 Running the Wind WizardChoice of MethodApplicability of the Low-Rise Building method

Running the Wind Wizard for ASCE/SEI 7-05Low Rise Buildings - GeometryRigid Buildings of All Heights - GeometryBasic Wind Data

Running the Wind Wizard for ASCE/SEI 7-10Low Rise Buildings - GeometryRigid Buildings of All Heights - GeometryBasic Wind Data

Results

Chapter 6 Creating Wind Zones on the BuildingASCE7-05 - Low Rise Building MethodDirectionsWall ZonesRoof ZonesAutomatic Zoning

ASCE7-05 - All Heights MethodDirectionsWall ZonesRoof ZonesAutomatic Zoning

ASCE7-10 - Low Rise Building MethodDirectionsWall ZonesRoof ZonesAutomatic Zoning

ASCE7-10 - All Heights MethodDirectionsWall ZonesRoof ZonesAutomatic Zoning

Chapter 7 Creating Wind LoadcasesTorsional LoadcasesAll Heights Method - Design Wind load Cases (ASCE7-05 Figure 6-9 & ASCE7-10 Figure 26.8-1)

Chapter 8 Load DecompositionRoofsWalls

Chapter 9 References

ASCE7-05 Wind Wizard Handbook

Documents

Transcript of ASCE7-05 Wind Wizard Handbook