This option is used to define the appropriate distances of member sections protected against lateral buckling, i.e. lateral buckling length. This option is made available by pressing one of the following buttons: Upper Flange or Lower Flange in the Lateral Buckling Parameters field of the Member Definition - Parameters dialog box.
At the bottom of the dialog box there is the Intermediate bracings option. Pressing the 
icon, which represents this option, opens the Internal bracings dialog box.