Innovative strengthening of 3d CHS truss joints with laser-cut techniques

• Full-scale tests on 3D trusses with and without reinforcing plates are presented. • FE models are validated against experiments. • Parametric studies examining a wide range of geometrical properties are performed. • Reinforced joints with double stiffeners achieve up to 30 % strength increase. • Stress analysis reveals ∼50 % reduction in weld stress in joints with stiffeners. This study investigates innovative reinforcement strategies for welded circular hollow section (CHS) 3D truss joints. An experimental campaign on three full-scale CHS joints, complemented by validation of the numerical model and an extensive parametric analysis of 84 cases, demonstrated that inserting internal stiffening plates with thickness equal to twice the chord wall thickness ( 2t₀ ) provides an effective and practical design rule across a wide range of geometries to avoid the failure of the joint, shifting collapse in the connected members. Reinforced joints exhibited significant strength improvements, up to 42.5 % higher compared to unreinforced configurations, and consistently redirected failure away from the joint itself to the adjoining chord member. The reinforcement techniques eliminated punching shear failure and enabled the use of thinner chord walls ( t₀ < t₁ ), providing a viable way to reduce material consumption and fabrication costs without compromising safety or performance. Parametric analyses confirmed that reinforced joints could also accommodate brace-to-chord gaps up to 1.5 times the chord diameter without compromising the resistance of the truss, extending the effective design range beyond current recommendations. Stress analyses further showed that the adopted reinforcement strategies reduced average stresses in the welds by approximately 55 %, with the crossed-plate configuration achieving the most uniform stress distribution and suggesting improved fatigue performance. These results demonstrate that advanced fabrication methods, such as laser cutting, can deliver more efficient, cost-effective, and architecturally integrated truss joint designs while maintaining high structural safety standards.