Thin-wall hollow torsion members with restrained ends (see Figure 6.20) may also
warp under torsion. However, in contrast to torsion members with simply connected cross
sections, noncircular thin-wall hollow torsion members may, under certain conditions,
twist without warping. A solution presented by von K h h and Chien (1946) for
constant-thickness hollow torsion members indicates that a torsion member with equilateral
polygon cross section does not warp. By contrast, if tl = t2, the rectangular section
hollow torsion member (a # b) in Figure 6.20 tends to warp when subjected to torsion
loads and, hence, to develop a normal stress distribution at a restrained end.