If the selected Specification is AASHTO 2015 (
) the following instructions
apply:
When the Edit or Add wind load option is selected the
dialog shown below will appear:
Fig. 1 Edit/Add
wind load options
Wind loading calculates the effective forces acting on the
bridge due to wind impact and is assumed to be uniformly distributed on the
area exposed to the wind. The implementation of wind load follows requirements
for Wind Load on Superstructure (WS) as described on AASHTO LRFD Article
3.8.1.2.
The wind pressure on the superstructure depends on the
wind angle and superstructure dimensions.
The wind angle is defined as the angle between the normal
to the longitudinal direction of the bridge and wind direction, positive angle
means the wind is blowing from the right side (normal to the member) and
negative angle means the wind is blowing from left side. See Wind Direction
figure below.
Fig. 2 Wind
Direction
If the selected Specification is AASHTO 2016 (
) the following instructions
apply:
| Setting | Description |
|---|
| Calculate Pz
|
Check this option to calculate the wind pressure (Pz)
based on the selections below
|
| User Input
|
Check this option to provide the pressure value Pz
directly. When this option is selected only the Load name and Pz fields can be
edited.
|
| Load Name
|
Enter the name to be used to reference the wind load
case
|
| Gust Effect Factor G
|
The default gust factor is 1.0. This value must be
>1.0
|
| Structure Height Z
|
Enter the structure height
|
| Drag Coefficient Cd
|
Enter the drag coefficient
|
| Ground Roughness
|
Select the ground roughness:
- B: Dense obstructions
- C: Scattered
obstructions
- D: Flat unobstructed
area
|
| Skew Angle
|
Select the skew angle of the bridge relative to the
bridge. See Figure 2 above
|
| Fascia Member(s)
|
Select the member (left or right fascia) to which the
wind load is applied
|
| Limit State
|
Select one of the 3 limit states to be used in the
pressure calculation:
- Strength III
- Strength V
- Service I
|
| 3-Sec Gust Wind Speed
|
Enter the 3-second gust wind speed. The default is 115
mph
|
| Pz
|
If Calculate Pz is selected above, this will be the
calculated pressure in psf.
|
If User Input is selected above, enter the desired
wind pressure in psf
|
| OK
|
Press OK to accept the changes and exit the dialog
|
| Cancel
|
Press Cancel to exit the dialog without accepting any
changes
|
