Numerical Simulation of Corner Reinforced Concrete Column-Beam Joint with Differential Concrete Grades and Steel Fibres Under Monotonic Loading

Structural elements are composed of joints that are essential for force transfer. In particular, for concrete structures, the column-beam joint is an integral section that requires insight due to the traditional use of different concrete grades, forming a strong-column-weak-beam (SCWB) system. A numerical model of the joint was developed in Abaqus to explore the axial load performance and damage tolerance of corner column-beam joints with different concrete grades under monotonic static loading. A concrete-damaged plasticity model (CDPM) was used to model the damage behaviour of concrete, utilising the available strain-stress models in literature and EuroCode 2. Results show that concrete column-beam joints with low grade (25 MPa) fail significantly compared to concrete cores with 30 MPa. In addition, an increase in concrete grade to 30 MPa in the joint increases the load-carrying capacity by 5.6% compared with the column joint with a concrete grade of 25 MPa. Therefore, using weak concrete joints results in axial high compressive stress exceeding the compressive strength limit, which may lead to cracks in the joint core and adjoining structural elements. It is recommended that structural engineers use the same grade for columns and beams, or use the lowest compressive strength in design, to prevent overloading the weak joint.