CADDtools ASCE 7-10 Wind Load Program by Howard Goding

A Wind load Pic

Here is a web enabled Asce7-10 wind load program. The program displays the Wall Components and Cladding design pressures for the selected conditions. I use these programs to verify the design pressures provided by the architects or to create them for estimating or engineering purposes. It is highly recommended you review the building code to understand where the information comes from. Refer to the bottom of this page for various building code web site links.

As you will see in the Asce 7-10 Building Code there are four parts for determining the components and cladding. This program utilizes Part 1: Low-Rise Buildings h<= 60 and Part 3: Buildings with h>60 ft to calculate the design pressures. The program will automatically determine Part 1 or Part 3. There are many references on the web about the big changes to the ASCE7-10 code. A few of the key changes are: The Importance factor used on the older code is no longer used and is built into the wind speed maps. The Wind speed maps are separated into category 1 through 4. Refer to your local jurisdictions to determine which map and wind speed to use. For me the biggest change utilizes the LRFD (Load Resistance Factor Design) and ASD (Allowable Stress Design). In general the LRFD will be used for the main structure and the ASD will be used on the components and cladding. In these calculations the ASD velocity pressure is reduced by 60%.

Since the introduction of the ASCE 7-16 code, I made a few revisions to the ASCE 7-10 program. I added a check box to force the program to utilize part 1 when using the exception rule in part 3 which allows the use of part 1 for heights greater then 60 feet and less than 90 feet. See the calculator below to verify the exception can be used. Finally, I added programing to accommodate the use of feet and inches to be converted to decimal feet as the program requires. This will cover the mean roof height and least building width. The program will let you know when the conversion has happened after the design pressures are calculated.

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Design Load Method: ASCE7-10 Strength Design Load & Allowable Stress Design

Wind speed = mph (required)
From Wind Speed Maps Figure 26.5

Building Exposure =
Defined from Table 26.9-1, page 256

Internal Pressure Coefficient =
From Table 26.11-1, page 258

Roof Angle =
From Figure 30.4-1, page 335

Kzt =
Kzt default = 1.00
Refer to section 26.8 and figure 26.8-1 to determine the wind speed-up effect. See below for additional information about Kzt.

Kd =
Kd default = 0.85
Refer to Table 26.6-1, page 250. See below for additional information about the Kd factor.

Mean Roof Height = ft (required)
Example 30'-6" is written as 30.5

Least Building width = ft
For determining Zone 5 dimension "a". Example 55'-8" is written as 55.67

Custom Tributary Area = sq feet
Enter an optional Tributary area between 10 and 500 square feet at (MRH <= 60 ft) or between 20 and 500 square feet at (MRH > 60 ft).

The following fields are optional and will show up on you printed page.

Project Name = optional

Company Name = optional

User Name = optional

E-mail = optional

Exception from part 3 page 320 (Use the calculator below)
If the mean roof height is greater then 60 and less then 90 - Part 1 can be used if the height-to-width ratio is 1 or less.
By checking the Exception box (Part 1) will be used to perform the calculations.


CADDtools Calculators

Check if Exception in Part 3 is applicable
(Enter decimal feet only. Example 62'-6" is written as 62.5 )
Enter Mean Roof Height: ft
Enter largest Building Width: ft



A note about the Kzt factor:

  • Kzt is a topographic effect factor to account for speed up over hills. Since I reside in Florida I use Kzt equals one and established that as the default value. Refer to your states Kzt values and adjust the value as required. I found a paper from the Florida International University stating "few places in the state of Florida would warrant an escarpment factor greater than 1.0, therefore Kzt is unnecessary in the current endeavor". I found a great site showing the Kzt factors for Seattle, Washington from the Department of Planning and Development, their values range from 1.12 to 2. Follow the link to the Seattle Washington website for information.

    • A note about the Kd factor:

  • Kd is a directionality factor. Over the years the Kd factor value has stirred up some controversy as to whether the value is 0.85 or should be one. I have set the default value to 0.85; if you are uncertain what value to use change the value to one for a worst case scenario.

    • A note about the Design Load Method:

  • The ASCE7-10 code utilizes the Strength Design Load also called (LRFD Load Resistance Design Load) method and the Allowable Stress Design Load (ASD) method. The Florida Building Code 2010 (FBC2010) utilizes an Ultimate Design Wind Speed Vult and Normal Design Wind Speed Vasd in lieu of LRFD and ASD. The FBC2010 uses a wind speed conversion where the Vasd is reduced by 60 percent; this happens by multiplying the Vult by (0.775 which is the square root of 0.6). Since the velocity pressure is reduced by 0.6 in the formula for ASCE7-10 and is reduced by 0.775 in the wind speed which is used in the velocity pressure formula for FBC2010 this makes the design pressures for both methods the same.

    • ASCE7-05 Design Load calculator

    Archived

    This is a link to an archived ASCE7-05 design pressure calculator. Follow the link to CADDtools ASCE7-05

    Links you may need

    This website funded by the sale of MetalOpt go to MetalOpt.com to purchase.

    American Society of Civil Engineers web site. Follow the link to ASCE.org

    This is the Florida Department of Community Affairs Building Code Information Systems web site. Here you can view the current Florida Building code. Follow the link to floridabuilding.org