Compressive Behavior of Damaged Tubular T-joints Retrofitted with Collar Plate

The static bearing capacity and failure modes of damaged tubular T-joints retrofitted with collar plates under axial compression were investigated. Two-step loading was applied: First, the chord deformation was loaded to the pre-designed degree, followed by unloading and collar plate installation. Subsequently, the specimens were reloaded. The maximum capacity and corresponding displacement (Delta(1,m)) were determined, and the ratio of the chord deformation of the other joints to Delta(1,m) was utilized to define the damage degree. The maximum capacity of retrofitted tubular T-joints could be up to 13-77% in second step loading, compared with that of unreinforced T-joints; however, the capacity decreased by 2-10% compared to that of directly reinforced T-joints. Sixty-nine finite element models were generated. The effects of chord wall thickness, chord diameters and collar plate lengths on the bearing capacity under different damage degrees were analyzed. A satisfactory effect could be obtained by using a suitable size of expanded collar plates under a constant damage degree. Retrofitting with collar plates could mitigate the development of equivalent plastic strain in the joint intersection, even for considerably damaged tubular T-joints. A modified formula considering the damage degree was proposed for bearing capacity prediction of retrofitted tubular T-joints.