EXPERIMENTAL COMPARISION OF STATIC BEHAVIOR OF TUBULAR N-JOINTS REINFORCED IN DIFFERENT WAYS

Static tests on a tubular N-joint (JD-A), a plate reinforced tubular N-joint(JD-B), a tubular N-joint with concrete filled in chord (JD-C) and a tubular N-joint reinforced by both concrete and plate(JD-D) under the axial compression of brace and chord were carried out. The failure modes, the relationship between loads in compressive brace and deformation in tubular wall of chord, the equivalent stress distributions in tubular wall of chord and ultimate capacity are compared between the four joints. It shows that different reinforced measures can cause different failure modes. The research indicates that the ultimate capacity of tubular joints can be remarkably enhanced by filling concrete in chord and can be only enhanced to a certain extent by the reinforced plate, While welding a reinforced plate on tubular wall of chord may weaken ultimate capacity of the joint when the radial stiffness of chord is sufficient. Finite element analysis (FEA) was made to validate the experimental results, and the calculation shows that analytical results agree well with the experimental results.