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ASCE 7 Wind Load dialog box

Used to generate a wind load per the ASCE 7 specification. Input data on the type of structure, surrounding terrain, and wind.

Opens when Calculate as per ASCE-7 is clicked on the Add New: Wind Definitions dialog box when Custom is selected as the type..

Using this feature, you can define different intensity vs. height data for the windward side, leeward side and side walls for a structure. Each can be defined as a different load type and then applied in the relevant direction with appropriate direction factor. The defined wind loading can then be applied to the structure following the usual method.

Note: For details on generation of wind load and command syntax, refer to TR.32.12.3 Generation of Wind Loads .

Common tab

SettingDescription
ASCE -7-

Select the version of the ASCE 7 (SEI/ANSI/ASCE 7 - Minimum Design Loads for Buildings and Other Structures) code to use: 1995, 2002, or 2010.

Building classification category

Select the building classification category, based on the nature of occupancy, as obtained from Table 1-1 in ANSI/ASCE 7-95 or SEI/ASCE 7-02.

Category can be I, II, III or IV.

Basic Wind Speed

Specify a basic wind speed as described in Figure 6-1 in the the ANSI/ASCE 7-95 code or in section 6.5.4 of the SEI/ASCE 7-02 code, along with units.

Wind speed is assumed to be the plotted or tabulated 3-second gust wind speed.

Exposure Category Select an exposure category as per section 6.5.3 in the ANSI/ASCE 7-95 code or section 6.5.6.3 of the SEI/ASCE 7-02 code.
Structure Type

Select the type or structure that best fits the model from the following:

  • Building structures
  • Chimneys, Tanks, and similar structures
  • Solid Signs — Used to generate wind loads on solid signs or walls and calculates the Cf factor per the selected code version.
  • Open Signs
  • Latticed Framework
  • Trussed Tower
Note: The data input tab changes to the selected structure type once the Apply button is clicked.
Consider Wind speed-up over hill or escarpment

Select Yes to consider wind speed-up over a hill or an escarpment and No to ignore it.

If there are isolated hills and escarpments that constitute abrupt changes in the general topography, the increase in speed can be considered as per clause 6.5.5 in the ANSI/ASCE 7-95 code or as per section 6.5.7 in the SEI/ASCE 7-02 code.

Type of Hill or Escarpment Select the type of hill, ridge or escarpment on which the structure is located, based on Figure 6-2 of ANSI/ASCE-7-95 code or on Figure 6-4 of the SEI/ASCE 7-02 code. The options available are 2-D Escarpment, 2-D Ridge and 3-D Axisymmetric Hill.
Height of Hill or Escarpment (H) Specify the height of the hill or escarpment relative to the upwind terrain (H in Figure 6-2 of the ANSI/ASCE-7-95 code or in Figure 6-4 of the SEI /ASCE-7-02 code).
Distance upwind of crest (Lh) Specify the distance upwind of crest to where the difference in general elevation is half the height of the hill or escarpment (Lh in Figure 6-2 of the ANSI/ASCE-7-95 code or in Figure 6-4 of the SEI/ASCE-7-02 code).
Distance from the crest to the building (x) Specify the distance from the crest to the building site.  A negative value signifies the distance is in the downwind direction (X in Figure 6-2 of the ANSI/ASCE-7-95 code or in Figure 6-4 of the SEI/ASCE-7-02 code).

<structure type> tab

When the structure type is changed on the Common tab, the list of parameters on the Main Building tab changes. The full list of parameters explained here is for the structure type of Building Structures. Those parameters that are different are explained below for each type of structure.   

Structure Type: Building Structures

SettingDescription
Building Height Specify the height above ground to the highest point on the roof surface, along with units.
Building Length along the direction of Wind (L) Length of building measured along the direction of wind.
Building Length Normal to the direction of Wind (B) Length of building measured normal to the direction of wind.
Building Natural Frequency Specify the natural frequency of the building to calculate Gust Effect Factor.
Building Damping Ratio Specify the damping ratio to calculate Gust Effect Factor.
Enclosure Classification

For ASCE 7-02, select the building classification as open, partially enclosed, or enclosed per the provisions of section 6.2 of SEI/ASCE 7-02.

Note: Not applicable for ASCE 7-95.
Kz Velocity Pressure exposure coefficient calculated as per Table 6-3 of the ANSI/ASCE-7-95 code or as per Table 6-3 of the SEI/ASCE-7-02 code.
Use Kzt

Select this option to specify a topographic factor value for wind speedup.

If not selected, the topographic factor is calculated and displayed. When wind speedup is considered, Kzt is calculated as per Eq 6-2 of the ANSI/ASCE-7-95 code or as per Eq 6-4 of the SEI/ASCE-7-02 code.

Use I

Select this option to specify an importance factor value.

If not selected, the importance factor is calculated and displayed. The importance factor used is as per Table 6-2 of the ANSI/ASCE-7-95 code or as per section 6.2 of the SEI/ASCE-7-02 code.

Use Kd

Select this option to specify a wind directionality factor.

If not selected, the wind directionality factor is calculated and displayed. The wind directionality factor is calculated as per Table 6-4 of the SEI/ASCE 7-02 code.

Note: Not applicable for ASCE 7-95.

Structure type : Chimney, Tank and similar Structures

SettingDescription
Height(H) Height of the structure as defined by the term "h" in Figure 6-19 of the SEI/ASCE 7-02 code.
Least Horizontal Dimension (W) Smaller of the plan dimensions. In case the cross section of the structure in plan is circular, the diameter needs to be specified.
Horizontal Cross-Section Type This is the cross section of the structure in plan as defined in Figure 6-19 of the SEI/ASCE 7-02 code. The available options include square with wind being normal to face or acting along the diagonal, hexagonal, octagonal and round.
Depth of protruding elements such as ribs and spoilers (D’) For round type cross sections, depth of protruding elements need to be defined which is a measure of the surface roughness as indicated in Figure 6-19 of the SEI/ASCE 7-02 code.

Structure type: Solid Signs

SettingDescription
Height (H) Height of the structure which is used for calculating the height to width ratio as defined by the term "v" in Figure 6-20 of the SEI/ASCE 7-02 code.
Horizontal Dimension of Sign (M) Horizontal dimension of the solid sign
Vertical Dimension of Sign (N)

Vertical dimension of the solid sign.

Note: If the sign is at the ground level, the height (H) and vertical dimension (N) should both be specified the same value.

Structure type: Open Signs / Lattice Frame Work

SettingDescription
Ratio of Solid Area to Gross Area Ratio of solid area to gross area as indicated by the term ∈ in Figure 6-21 of the SEI/ASCE 7-02 code.
Orientation of the members exposed to wind The type of member surfaces which are exposed to wind. Select flat-sided members or rounded members in Figure 6-21 of the SEI/ASCE 7-02 code.
Diameter of typical round member Diameter for round members as defined by the term "D" in Figure 6-21 of the SEI/ASCE 7-02 code.

Structure type : Trussed Tower

SettingDescription
Horizontal Cross Section

The type of cross section of the tower in plan as defined in Figure 6-22 of the SEI/ASCE 7-02 code. The available options include square and triangle.

Building Design Pressure tab

SettingDescription
Building Wall to generate Wind Load on:

Select the side of the structure, with respect to wind direction, for which you wish to generate a wind load. The pressure will be calculated as per Table 6-1 of the ANSI/ASCE-7-95 code or as per Equation 6-23 of the SEI/ASCE-7-02 code, based on the code selection made on the /span> tab. The relevant equation will also be displayed below.

  • Windward - Used to generate the design wind pressure for the windward side.
  • Leeward - Used to generate the design wind pressure for the side wall.
  • Side Wall - Used to generate the design wind pressure for the side wall.
Note: The pressure profile for each of the building walls has to be individually determined under a unique load type number. Thus, generating the profile for the three sides of the building constitutes three separate steps and thus, three separate types. Each type can then be applied with one load case or separate load cases and then applied in the relevant direction with the appropriate direction factor. Examples illustrating wind load generation can be found in the examples manual.
Use G

Select this option to specify a gust effect factor value.

If not selected, the Gust effect factor is calculated and displayed. The gust effect factor is calculated as per Table 6-1 of the ANSI/ASCE-7-95 code or as per section 6.5.8 of the SEI/ASCE-7-02 code, based on the code selection made on the Common tab.

Use Cp

Select this option to specify a wall pressure coefficient value.

If not selected, the wall pressure coefficient is calculated and displayed. The wall pressure coefficient is calculated as per as per Fig 6-3 of the ANSI/ASCE-7-95 code or as per Figures 6-11 through 6-17 of the SEI/ASCE-7-02 code, based on the code selection made on the Common tab.

Use GCpi

Select this option to specify an internal pressure coefficient value.

If not selected, the internal pressure coefficient is calculated and displayed. The internal pressure coefficient is calculated as per as per Table 6-4 of the ANSI/ASCE-7-95 code or as per Figure 6-5 of the SEI/ASCE-7-02 code, based on the code selection made on the Common tab.

Use Cf

Select this option to specify a force coefficient value used for structures other than buildings. If not selected, the force coefficient is calculated and displayed as follows:

  • For Chimney, Tank, and similar structures: Calculated as per Figure 6-19 of the SEI/ASCE 7-02 code.
  • For Solid signs: Calculated as per Figure 6-20 of the SEI/ASCE 7-02 code.

The force coefficient is used for the calculation of the design pressure.

Height vs. Intensity table

Displays the generated wind profile based on the current input in the dialog.

SettingDescription
OK Accepts the current Height vs. Intensity table values displayed on the Building Design Pressure tab and applies them to the Add New: Wind Definitions dialog.
Apply Applies changes made in one of the dialog tabs to other tabs for use (e.g., the code selection was changed).
Cancel Closes the dialog without adding an ASCE wind definition.
Help Opens the STAAD.Pro Help window.