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.
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 22.214.171.124 of the SEI/ASCE 7-02 code.|
Select the type or structure that best fits the model from the following:
|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
|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.|
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.
|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.|
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.
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.
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.
Structure type : Chimney, Tank and similar Structures
|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
|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.
Structure type: Open Signs / Lattice Frame Work
|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
|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
|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.|