Integrated design framework of 3D printed planar stainless tubular joint: Modelling, optimization, manufacturing, and experiment

Abstract Nowadays, tubular joints with superior structural properties have been extensively applied in constructing the complicated multi-planar steel joints that are often adopted in the grid shell structure system. However, sometimes it is challenging to maintain high-quality on-site welding joints or even difficult to assess the quality of on-site welding, especially for the overhead welding. This paper presents an integrated design framework of the 3D printed planar stainless tubular joint, and this framework is implemented by Solid Isotropic Material with Penalization Method (SIMP). Three joints with different brace to chord width ratios are optimized, and the re-engineered joints are obtained using computer-aided design software. Joints independently designed and manufactured by 3D printing methods can be riveted with other structural members to simplify the installation process and improve the construction efficiency, thus reducing the difficulty of on-site welding. Non-contact 2D DIC (Digital Image Correlation) is used to analyze the strain distribution more intuitively for 3D printed and welding planar tubular joints. Moreover, the coupon tensile test is proposed to analyze the stress–strain relationship when considering different printing orientations. Experiments show that the orientation of material additive manufacturing affects the yield strength, ultimate strength and elongation at fracture to a certain extent but has little influence on Young’s modulus. The optimized joint exhibits different failure modes than the traditional tubular joints, which can achieve strong-joint and weak-component mechanisms and avoid failure of the entire joint when local damage occurred. In addition, the plump curve according to the hysteresis loop suggests that the energy dissipation of the optimized joint is larger than the traditional welding joint, which is beneficial to enhance the seismic performance of the structures. The developed framework can also be extended to the complex spatial joints, which is subjected to multi-planar loads in the future.