7/29/2019 Wind Loadpages From c2tr

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6-24 Technical Discussions

Wind Loads

Wind loads are generated by multiplying the pipe exposed area, including insulation, and considering angle to the wind, by

the equivalent wind pressure and the pipe shape factor. There are typically three different ways to get at the equivalent wind

pressure:

ASCE #7 (1995)

Pressure vs. elevation table entry

Velocity vs. elevation table entry

The total wind force on the element is calculated from

F = PeqSA

Where:

F = the total wind force on the element

Peq = the equivalent wind pressure (dynamic pressure)

S = the pipe elementwind shape factor

A = the pipe element exposed area as shown in the figure as follows:

Peq is calculated for each end of the element and the average taken. The average applies uniformly over the whole length of

the element. Note, the wind force is applied in the three global directions as a function of the element direction cosines.

If the user enters a velocity vs. elevation table then the velocity is converted to a dynamic pressure using the following

equation:

P = 1/2 V2 where V is the wind velocity and is the air density.

The WIND SHAPE FACTOR is entered on the pipe spreadsheet and, for cylindrical elements, the value from Table 12 is

between 0.5 and 0.7. A value of 0.65 is typical. The wind shape factor as entered is distributive.This means that the

shape factor applies for all following elements until zeroed or changed.

Important: The user does not have to enter the shape factor on each pipe spreadsheet. Zero (or turn "Off") the wind

shape factor if the piping system runs inside of building or similarly protective structure.

Wind load data is entered on the Wind Loads (on page 3-61) tab of the Static Load Case Builder. Up to four different wind

loads can be entered per analysis. These typically might be set up to model wind loads in the +X, -Y, and -Z directions.

The ASCE #7 ( 1995) Method for computing equivalent pressure requires several computerized table look ups and

interpolation. The user enters the following parameters:

1 Basic wind speed(mph) - The minimum allowed basic wind speed is 85 mph. This does not include averages for

abnormally high wind loading events such as hurricanes or tornadoes.

ASCE #7 refers to fig. 6-1 for basic wind speeds in the continental United States. The following description is a crude

representation of Figure 1:

California 85 mph (124.6 ft/sec)

Other West Coast Areas 85 mph (124.6 ft/sec)

Great Plains 90 mph (132.0 ft/sec)

Non-Coastal Eastern United States 90 mph (132.0 ft/sec)

Gulf Coast 130 mph (190.6 ft/sec)