This option is used to define the appropriate distances of member sections protected against torsion, i.e. lateral buckling length. This option is available after 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.