Experimental study on stress concentration characteristics of joints in concrete-filled rectangular steel tubular truss

In order to investigate the fatigue behavior of the joint in concrete-filled rectangular steel tubular composite truss bridges, two girders were tested in three-point bending, and then the stress concentration factor in their K-joints was measured and analyzed. Meanwhile, the applicability of the existing stress concentration factor equations for K-joints were validated through comparisons agianst the test results. The results show that using the prestressed concrete slab and shear studs to locally release shear action can effectively improve the cracking load, compared to the structure using reinforcement concrete slab and conventional shear studs. However, using the prestressed concrete slab and shear studs does not have contributions to ultimate bearing capacity. The joints in the two specimens have similar hot spot stress distributions in the brace with the maximum values at the tensile brace toe. Due to the differences in concrete slab and studs, the joints in the two specimens have different hot spot stress distributions in the chord with the maximum values at tensile brace toe. The validation analysis of the existing stress concentration factor equations for K-joints demonstrates that the equations recommended by Mang et al would underestimate the stress concentration factors. The equations suggested by Soh et al and CIDECT design guide would overestimate the stress concentration factors. The equations recommended by Puthli et al would overestimate the maximum stress concentration factor at the location of tensile brace, and underestimate the maximum stress concentration at the location of compressive brace and chord. The results calculated using the equations proposed by Jiang et al have the best agreement with the test results. © 2022, Editorial Office of Journal of Building Structures. All right reserved.