Design Method and Force Transmission Mechanism of 3D Printed Concrete Truss Beams Reinforced with 3D Conical Reinforcement (2025-09)¶

3D printed concrete truss structures using horizontal or planar reinforcement represent a widely adopted construction approach, offering benefits including lightweight characteristics, printing simplicity, and satisfactory load-bearing performance. However, the layer-by-layer manufacturing process creates interfacial incompatibility between reinforcement and printed concrete matrices due to insufficient transverse connectivity, ultimately affecting structural reliability. This research presents an innovative 3D conical reinforcement system designed to improve the mechanical behavior of reinforced 3D printed concrete truss beams through enhanced load transfer efficiency. Experimental investigations involving 10 beam specimens were conducted to examine the effects of: (1) planar reinforcement ratio, (2) 3D conical reinforcement configuration, and (3) shear-span ratio on structural performance characteristics. Test results indicated that the presence of 3D conical reinforcement enhanced the ultimate shear capacity by up to 15 % and increased post-peak deformation capacity by over 40 % relative to conventional 2D reinforcement systems. The study also established the refined finite element models (FEM) accounting for material anisotropy and interfacial bond behavior to elucidate the beam load transfer mechanisms. Furthermore, a modified shear capacity calculation model was established by integrating both 2D reinforcement shear-lag effects and 3D conical reinforcement contributions into reinforced concrete design equations, which demonstrates good correlation with experimental measurements.