Shear-lag phenomenon in framed tube structures with multiple internal tubes

A simple numerical modelling technique is proposed for estimating the shear-lag effects of tube(s)-in-tube structures. The proposed method idealises the framed-tube structures with multiple internal tubes as equivalent multiple tubes (i.e. box beams), each composed of four equivalent orthotropic plate panels. Hence, the tube(s)-in-tube system can be analysed using an analogy approach where each tube is individually modelled by a box beam that can account for the flexural and shear deformations as well as the shear-lag effects. The numerical analysis of shear-lag is based on the minimum potential energy principle in conjunction with the variational approach. In the paper, the additional bending stresses and the sheer-lag reversal points are also investigated to estimate the shear-lag behaviour of such a system.