Stress concentration factors in FRP-reinforced tubular DKT joints under axial loads

The stress concentration factors (SCFs) in uniplanar fibre-reinforced polymer (FRP) DKT joints are calculated under five axial loading conditions to determine the maximum SCFs. To this end, 108 finite element models of reinforced DKT joints with different FRPs and geometrical parameters are analysed. Available experimental data and formulas are used to validate the finite element models. The validated finite element models are utilized to investigate the effects of the FRP parameters along with different geometrical parameters on the stress concentration factors in uniplanar DKT joints. The simulations show a reduction of the maximum SCF by around 40% compared to unreinforced DKT joints. The reduction effect increases significantly with increasing the FRP thickness and the number of layers. Despite the notable efficacy of the FRP sheets on the drop of the SCFs in the X-connections, there is not any study or equation on the X-joints with FRP. Therefore, a precise equation is proposed for quantifying the SCFs in X-connections with FRP and is checked against the UK DoE acceptance standard.