How do you design vehicle structure to meet roof crush requirements while minimizing mass?

Roof crush design (FMVSS 216, IIHS) requires supporting 3-4x vehicle weight with <127mm intrusion. Strategy involves: 1) A/B/C pillar optimization - high-strength steels (>1000 MPa), optimized sections for bending and axial loading; 2) Roof rail and header design - load path continuity, appropriate gauge distribution; 3) Joint design - maximizing moment capacity at pillar-rail connections; 4) Roof panel contribution - geometry and material selection; 5) Load path understanding - quasi-static loading mechanism differs from dynamic roof plunge. CAE optimization uses design of experiments to find minimum mass meeting criteria on both driver and passenger sides. Mass-efficient design exploits load path efficiency rather than adding material uniformly. Testing validates peak force and displacement at both initial contact and after intrusion limits.