Tensile tests of welded hollow spherical joints reinforced by CFRPs

To improve the tensile strength of welded hollow spherical joints (WHSJs) while maintaining their original structural configuration, a carbon fibre reinforced polymer (CFRP) is proposed in an innovative layered strengthening method. To assess the effect of varying the number of axial and circumferential CFRP layers on tensile properties, axial tensile tests were performed on 12 full-size Q235B WHSJs reinforced with CFRP. The experimental findings revealed that bonding the CFRP layers to the surfaces of the joints substantially increased their tensile strengths. Furthermore, with an increase in the number of layers, the resistance of the reinforced joints improved significantly, showing a proportional increase of 19.85%. The number of layers in the circumferential CFRP at the end anchorage was crucial for enhancing the axial tensile strength. By integrating the resistance equations for welded hollow spheres with those applicable to CFRP, new equations were derived for the resistance of CFRP-reinforced WHSJs. Additionally, the force analysis of circumferential CFRP led to the development of a simplified design formula to determine the optimal number of circumferential CFRP layers.