Several stress-strain models were used to predict the strengths of steel fiber reinforced concrete, which are distinctive of the material. However, insufficient research has been done on the influence of hybrid fiber combinations (comprising two or more distinct fibers) on the characteristics of concrete. For this reason, the researchers conducted an experimental program to determine the stress-strain relationship of 30 concrete samples reinforced with two distinct fibers (a hybrid of polyvinyl alcohol and steel fibers), with compressive strengths ranging from 40 to 120 MPa. A total of 80% of the experimental results were used to develop a new empirical stress-strain model, which was accomplished through the application of the particle swarm optimization (PSO) technique. It was discovered in this investigation that the new stress-strain model predictions are consistent with the remaining 20% of the experimental stress-strain curves obtained. Case studies of hybrid–fiber–reinforced concrete constructions were investigated in order to better understand the behavior of such elements. The data revealed that the proposed model has the highest absolute relative error (ARE) frequencies (ARE 10%) and the lowest absolute relative error (ARE > 15%) frequencies (ARE > 15%).

Salient features of lightweight aggregate concrete (LAC) include noticeable fire resistance, high strength-to-weight ratio, and low magnitude of dead loads. Further, LAC has a low cost, eases construction practices, and possesses an environment-friendly nature. On the downside, LAC has substandard mechanical properties in comparison to normal aggregate concrete. Natural fiber-reinforced polymers (FRPs) have shown their potential in ameliorating the mechanical properties of natural aggregate concrete. So far, no study has been conducted to assess the efficacy of hemp rope confinement to strengthen lightweight aggregate concrete especially comprising rectilinear sections. This study aimed to overcome the substandard nature of LAC. A low-cost, sustainable, and environmentally green solution in the form of natural hemp rope layers is proposed. Twenty-four square concrete specimens were tested in three groups depending upon the presence and quantity of lightweight aggregates. It was found that concrete constructed with lightweight aggregates demonstrated lower ultimate compressive strength and strain as compared to normal aggregate concrete. Hemp rope-confined LAC showed enhanced ultimate compressive strength and strain. This enhancement was found to increase with the number of hemp rope layers. Several existing ultimate stress models were assessed to predict the ultimate compressive strength of the hemp rope-confined specimens. Only a single model was able to predict the ultimate compressive strength of the hemp rope-confined specimens with reasonable accuracy.