A Novel Steel Reinforcement Scheme for 3D Printed Concrete Beams: A Study on Shear Behaviour

Abstract

A Master of Science thesis in Civil Engineering by Mohamed Ashraf Khalifa entitled, “A Novel Steel Reinforcement Scheme for 3D Printed Concrete Beams: A Study on Shear Behaviour”, submitted in June 2025. Thesis advisor is Dr. Adil Tamimi and thesis co-advisor is Dr. Sami Tabsh. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This thesis presents an innovative steel reinforcement scheme for 3D Printed Concrete (3DPC) beams, developed to enhance structural performance while maintaining compatibility with the 3D Concrete Printing (3DCP) automated construction technology. The proposed reinforcement system integrates U-shaped structural steel channels with welded shear studs directly into the printing process to develop a composite beam system that eliminates the need for conventional formwork or manual reinforcement placement. A total of twenty shallow beams were fabricated using a robotic-arm extrusion printer and tested under both three-point and four-point static loading configurations to assess the influence of key study parameters such as beam width and height, channel geometry and orientation, and level of composite interaction on the shear behaviour. Experimental results confirmed that the proposed reinforcement scheme significantly increased shear strength, improved ductility, and enhanced residual load capacity, all whilst supporting full-autonomous construction. The beam tested beam specimens exhibited an average Ductility Index (η) of 2.3, an average Energy Dissipation Factor (EDF) of 2.9, and more than one-half of them demonstrated a Residual Capacity Factor (RCF) exceeding 50% at twice the displacement at peak load, indicating substantial deformation capacity and continued load resistance beyond failure. This study establishes that the integration of structural steel channels into 3DPC beams offers an automation-friendly solution to the longstanding challenge of reinforcement in 3DPC structures. A theoretical model based on the principles of mechanics of materials was also considered to determine the fraction of the shear strength contributions by the printed concrete and structural steel channel in resisting the applied load effect. The model demonstrated that the steel reinforcement accounted for an average of 7.5% of the total shear capacity of the composite sections considered in this study. Two predictive analytical models are proposed for the shear strength of 3DPC beams reinforced by steel channels with welded shear studs: one implicitly includes the contribution of the steel channel to shear resistance within that of the concrete, while the other explicitly quantifies the shear contribution of the steel channel.College of EngineeringDepartment of Civil EngineeringBachelor of Science in Civil Engineering (BSCE