Function
- Enter the laterally unbraced length of the compression side flange when acting on the unbraced length and bending moment for the member axis (y-Axis) and z-Axis of the member.
This function is automatically calculated by the program in consideration of the connection state (joint state, support condition) of the member, the non-support length for the y-Axis and z-Axis of the member when the member is designated by the Member Assignment.
Call
From the main menu, select [Rating] tab > [Type : Steel Bridge] > [Rating Input Data] group > [Rating Parameters] > [Unbraced Length(L,LB)]
Input
First, select the members in the model, and then enter the following:
Unbraced Length(L,Lb) dialog box
Option
Select Add/Replace or Delete.
Add/Replace :Add the newly entered values or update the previously entered values.
Delete : Delete the entered values. Data entry is not required when deleting.
Unbraced Length
Enter the unbraced lengths for the selected members' strong and weak axes.
Ly : Unbraced length for buckling about strong axis
Lz : Unbraced length for buckling about weak axis
Laterally Unbraced Length
Enter the laterally unbraced lengths.
Lb : Laterally unbraced length [Default = Lz]
Do not consider : Select this item, if the allowable bending stress computation about the member`s strong axis is to neglect the laterally unbraced length.
Input Method
There are two entry methods.
<Method 1>
Enter the values directly in the Ly, Lz, and Lb fields.
<Method 2>
Click the Ly, Lz or Lb field and select two nodes in the model. The straight distance between the two nodes is automatically calculated and entered..
Apply : Apply the entered values to the selected members.
Close : Close the entry Dialog Bar.
For members where the values of Ly and Lz have not been entered, the member lengths calculated by the program based on the nodal coordinates of the relevant beam (truss) elements are applied as the values of Ly and Lz. For members where the values of Lb have not been entered, Lz values are set to Lb. If "All Beams/Girders are Laterally Braced" option is selected in the Steel Design Code dialog box, this item is automatically selected and Lb=0 is automatically set by default. If the values of Ly, Lz and Lb are repeatedly entered for the same member, the values will be updated to the last values entered.
The entered unbraced lengths and laterally unbraced lengths can be reviewed in the data table arranged in the order of element numbers. The user may Modify/Add and Delete items in the data table.
Access the data table following the procedure below.
from the Main Menu select Design > General Design Parameter > Unbraced Length (L,Lb)
From the Tables tab in the Tree Menu select Design Tables > General Design Table > Unbraced Length (L,Lb).