Damage evaluation in gap tubular truss ‘K’ bridge joints using SFEM

•The smooth finite element analysis is used to enhance the accuracy of the results.•Simulation of accurate location of braces for best results is performed.•Effect of damage due to cracks on stress concentration factors (SCFS) was studied.•It is found that combined effect of inaccurate location of brace spacing and damage due to cracks reduce the strength of the joint rapidly.

A damage stiffness parameter α of the shell element is calculated analytically using the fracture mechanics concept. A smooth quad T4 element was modified using the calculated parameter α. The modified element was introduced at the junction between the chord/brace connection where welding defect had taken place, while the unmodified same element was used elsewhere on the joint. Thereafter, a finite element analysis was carried out using thin shell theory and the smooth element formulation to investigate the effect of brace spacing on the distribution of stress concentrations in the welded tubular ‘K’ joint. This was done in order to investigate the level of stress concentrations and damage in the welded connection in the tubular joint. The joint was first modelled with no gap between the braces and a finite element computer run was made. Thereafter, the joint was modelled with brace gaps from 10 mm to 70 mm and finite element computer runs were made. The results obtained were then compared with those published in the literature. It was found that the presence of variable gaps between braces of the joint together with pre-crack affects the strength of tubular ‘K’ joints appreciably.