The structural assembly (200) has box (202) having fiber sections (212,214) which are connected to each other at a crossing point (216). The fiber portion (212) has sub portions (218,220) which are connected to sub portions (232,233) of exterior wall (204) of box. The fiber section (214) has inner and outer ribs (222,224) which extend to inner and outer space (208) of box. A load (230) applied on attachment point (226) formed in outer rib is transferred by fiber section (214) to support element while another load (235) is transferred between sub portions (232,233) by fiber section (212). An independent claim is included for method for manufacture of structural assembly.