Cross Section TypesEdit
In the BD, there are two types of cross sections members can have. These are Tube (hollow) and Bar (solid). Here's the general rule to remember: If it's red (carrying compression), make it a tube; if it's blue (carrying tension), make it a bar. The following subsections explain this rule.
TubeEditTubes are hollow members. For a given weight and type of material, tubes are more expensive than bars, but tubes carry compression much more efficiently. Therefore, it is generally better to use tubes for members that sustain more compression than tension (red members).
Bars are solid members. For a given weight and type of material, hollow tubes and solid bars carry tension with equal efficiency. Since tubes are more expensive than bars, it is generally better to use solid bars for members that sustain more tension than compression (blue members).