Testing, analysis and design of wire and arc additively manufactured steel bolted connections

Capitalizing on Wire and Arc Additive Manufacturing (WAAM), 3D printed steel has shown significant potential in manufacturing large-scale steel structural elements in the construction industry. Due to the intrinsic difference in material properties, the mechanical performance of WAAM steel connections requires further investigation. In this paper, a total number of 24 WAAM steel coupon specimens with three different print layer orientations and 36 WAAM single-shear bolted connection specimens with one bolt of different design configurations were fabricated, dimensionally measured with 3D scanning technique, and tested under monotonic tension. The failure modes and ultimate capacities of the bolted connections were analysed, focusing on the print layer orientations of the WAAM steel plates. The current codified design provisions and design approaches proposed in the literature for steel structures were further evaluated by comparing the failure modes and ultimate capacities of the bolted connection specimens. This research shows that specimens with different print layer orientations present anisotropy phenomena in the coupon tests and bolted connection tests with differences of up to 10% and 20%, respectively. The relatively accurate predictions of the ultimate capacity of the WAAM steel bolted connection specimens following the current steel design standards are significantly compromised by predicting the incorrect failure modes, which could be attributed to the influence of anisotropic material properties of the WAAM steel plates and the failure modes of tilt-bearing and the end-splitting not being considered in current design provisions. This research conducted systematic experimental investigations focusing on the material properties of WAAM steel and the structural behaviours of WAAM single-shear bolted connections, which could potentially promote the application of WAAM technology in construction industry.