Closed-type links for torsion
Here is an interesting question posed by Mr L. Wadsworth: Clause 3.3.7 of CPllO requires that ‘closed-type links similar to bending code 74 of BS4466 should be used to resist torsion, presumably in preference to an ordinary code 60 link which, of course, is normally employed to resist shear. My query is-why? What is it about torsion
on a concrete beam that requires the use of a code 74 instead of a code 60 link? To my simple mind, the leg of a link is a simple filament, only capable of carrying tension; how does it know whether this tension arises from shear, torsion, or indeed anything else? Conversely, if a code 60 link is for some reason unable to resist the tension induced by a twist of the section, how then is it able to carry safely the tension induced by a shear force?