Typical Stamped B-Pillar Construction

Today’s typical B-Pillar construction involves three parts; the body side inner, B-Pillar reinforcement and body side outer as shown here.

In some instances other local reinforcements may be added, but let’s stick to a three-piece construction. Taking a section through the tumble home area in the z-plane, the typical cross section looks like what is
shown here.

In this view, the long fore-aft walls are the walls that are of concern when it comes to structural performance (buckling). Under roof crush loads, the body side inner is in compression. In a side impact, the B-Pillar reinforcement and body side outer are in compression.