Stress concentration factors test of reinforced concrete-filled tubular Y-joints under in-plane bending

To study the stress concentration factors (SCFs) of concrete-filled tubular Y-joints subject to in-plane bending, experiments were used to investigate the hot spot stress distribution along the intersection between chord and brace. Three concrete-filled tubular chords forming Y-joints were tested with different reinforcing components, including doubler-plate, sleeve, and haunch-plate reinforcement. In addition, an unreinforced joint was also tested for comparison. Test results indicate that the three different forms of reinforcement effectively reduce the peak SCFs compared with the unreinforced joint. The current research suggests that the linear extrapolation method can be used for chords, whereas the quadratic extrapolation method must be used for braces. The SCF is effectively reduced and more evenly distributed when the value of the axial compression ratio in the chord is increased. Furthermore, the SCFs obtained from the test results were compared to predictions from some well-established SCF equations. Generally, the predictions from those equations are very consistent for braces, but very conservative for concretefilled chords.