C-HCommentary — Chapter H Design of members for combined forces and torsion

Chapter H includes the following major changes and additions in this edition of the Specification:

• (1) Provisions have been added for hollow structural sections (HSS) subjected to combined forces to include biaxial bending and shear.
• (2) Section H4 has clarified that the holes being considered are bolt holes.

Chapters D, E, F, and G of this Specification address members subjected to only one type of force: axial tension, axial compression, flexure, and shear, respectively, or to multiple forces that can be treated as only one type of force. This chapter addresses members subjected to a combination of two or more of these individual forces, as well as possibly by additional forces due to torsion. The provisions fall into two categories: (a) the majority of the cases that can be handled by an interaction equation involving sums of ratios of required strengths to available strengths; and (b) cases where the stresses due to the applied forces are added and compared to limiting buckling or yield stresses. Designers will have to consult the provisions of Sections H2 and H3 only in rarely occurring cases.

• H1 DOUBLY AND SINGLY SYMMETRIC MEMBERS SUBJECTED TO FLEXURE AND AXIAL FORCE
• H2 UNSYMMETRIC AND OTHER MEMBERS SUBJECTED TO FLEXURE AND AXIAL FORCE
• H3 MEMBERS SUBJECTED TO TORSION AND COMBINED TORSION, FLEXURE, SHEAR, AND/OR AXIAL FORCE
• H4 RUPTURE OF FLANGES WITH BOLT HOLES AND SUBJECTED TO TENSION