Case Studies in Construction Materials (Jul 2024)
Structural efficiency of fly-ash based concrete beam-column joint reinforced by hybrid GFRP and steel bars
Abstract
In this paper, the structural performance of exterior fly-ash based concrete beam-column joints reinforced with hybrid glass fiber reinforced polymer (GFRP) and steel bars was studied, to inspect the hybrid concept efficiency under lateral loads. This paper studied two mixes of concrete, normal strength concrete (NC) and fly-ash based concrete (FC), a 20% replacement ratio of the cement weight with superplasticizer is considered in FC mix, which is considered as an environmental-friendly and cost-effective alternative to ordinary Portland cement. Ten joints were tested under the effect of monotonic lateral load experimentally. The studied joints were divided into two groups based on their concrete type, in each group, five joints with different GFRP to steel ratios “from 0% to 100% with an increment of 25%” were tested. The obtained results showed that the fly ash presence in concrete resulted in an average increase in both ductility and load capacity of 18% and 28.3%, respectively. Also, the average total energy absorption increased by 35%, and the average initial and post-yield stiffness increased by 34% and 41%, respectively. Moreover, the ductility index for each model was obtained, the FC model with 75% GFRP to steel ratio achieved the maximum ductility index, so it was considered as the optimum one. After that, the finite element analysis FEA was utilized to study the performance of the tested beam-column joints. The FEA showed identical results compared to the experimental ones concerning energy absorption, load capacity, and model stiffness. Finally, using FEA, a deep parametric study on FC models reinforced with GFRP to steel bars ranging from 60% to 90% was performed to obtain the optimum GFRP to steel reinforcement ratio. Through the performed parametric study, it was found that the optimum range of the reinforcement ratio was 68% to 82%. According to this research, the usage of fly ash in concrete increased RC beam-column joints' efficiency especially when provided with hybrid GFRP and steel reinforcement, in addition to the important environmental impact achieved through the recycling process. It was recommended to utilize the composite reinforcement ranging between 60% to 75% GFRP to steel bars in the presence of fly ash-based concrete for the beam-column joints.
