“…This is akin to a Timoshenko beam formulation (Wang et al 2000); when q s = q t and q f = q t , shear strains are developed and allow the potential for modelling simultaneous LTB and local buckling. Previous work on this type of interactive buckling has included experimental work combined with the effective width theory (Cherry 1960), some phenomenological modelling using rigid links and springs along with experiments (Menken et al 1991), some numerical work using a finite strip formulation ) and a finiteelement formulation (Menken et al 1997). To model this analytically, however, two displacement functions to account for the extra in-plane displacement u and out-of-plane displacement w from local buckling, see figure 2c,d, need to be defined.…”