Bulb-girder cross sections, such as that shown in Figure 1, may be created using the Section Designer.
Figure 1 - Bulb-girder cross section
To model a bulb-girder section, first open the Section Designer, then use polygons to draw the outline of the section without the corner radius, as shown in Figure 2:
Figure 2 - Outline without the corner radius
Next, switch to reshape mode by selecting Draw > Reshape Mode. Click on the section, then right-click on each corner joint to specify a radius where needed, as shown in Figure 3:
Figure 3 - Creating radial chamfers
Figure 4 presents the final bulb-girder cross section. All corners other than those at the extreme fibers are properly modeled with round corners.
Figure 4 - Final cross-section