Structural Performance Evaluation of Hexagonal and Pentagonal Reinforcement Bars Through FEA-Based Topology Optimisation under Multi-Load Scenarios

Abstract

The geometry of the reinforcement has a significant effect on the structural economy, rigidity, and economy of reinforcing material usage of reinforced concrete structures. In this study, the structural performance of conventional and topology-optimized hexagonal and pentagonal reinforcement bars is evaluated to design lightweight, sustainable and cost-effective reinforcement systems. Finite Element Analysis (FEA) and topology optimization were carried out on two Fe500 steel, two CFRP, two GFRP, and two Ti reinforcement bars with 10kN loading applied in the axial direction. The optimized hollow reinforcement bars were then used to construct reinforced concrete beams for testing, which included 100kN point load, 10kN/m uniformly distributed load, different linear load (0-20kN/m), and combined loading. The optimised hollows resulted in about a 20% reduction in material and cost with the same structural integrity. The stress increment of hexagonal hollow bars was only 12.76%-18.97% more than the solid bars, while a higher stress increment of 70.54%-82.72% was observed in pentagonal bars. Under combined loading, the modified Fe500 hexagonal reinforcement was able to withstand a maximum stress of 126.84 MPa with a displacement of 0.838 mm, showing that an economic analysis would yield annual savings of up to ₹5,43,600 per 1000m for the use of titanium reinforcement. The topology-optimized hexagonal reinforcement appeared to be a reliable alternative to the standard solid reinforcement for reinforced concrete structures, showing the best performance in terms of strength, stiffness, sustainability and economy.