## 5 Conclusions  
The influencing role of compressive strength and fiber content on the energy dissipation and ductility performance of high-strength fiber-reinforced concrete was investigated in this research using an integrated experimental and numerical approach. The results identify the optimizing role of fiber content for achieving enhanced structural performance under loading while revealing the moderating role of compressive strength on fiber effectiveness. The numerical modeling results agreed with the test data, supporting that the fibers can enhance plastic energy capacity to be absorbed by concrete specimens. With 90 MPa and 120 MPa concrete, adding fibers brought large amounts of increased energy absorption compared to normal concrete. However, the relationship between fiber weight ratio (FWR) and energy dissipation was non-linear, emphasizing the importance of identifying an optimal fiber content. The previous experimental measurements had shown FWR = 30 kg/m\({}^{3}\) to be the optimum. However, the sophisticated simulations showed a refined optimum at FWR = 27.5 kg/m\({}^{3}\) for both concrete types. This finding emphasizes the need for numerical modeling in optimizing a material quantity within tighter incremental ranges than experimentation permits. At the optimized FWR value of 27.5 kg/m\({}^{3}\), the maximum simulated energy absorption achieved was 5.87 kNm/m for 120 MPa concrete and 1.82 kNm/m for 90 MPa concrete. The compressive strength effect was expressed in the rate and extent of change in energy dissipation. The initial fiber addition from 0 to 20 kg/m\({}^{3}\) produced a more significant relative increase (\(-\)339%) in the 90 MPa concrete than in the 120 MPa concrete (\(-\)188%), suggesting that fibers are more important in increasing the ductility of lower-strength concrete. Despite that, all the total energy dissipation values were greater in 120 MPa concrete at each FWR level. Beyond the limiting FWR of 27.5 kg/m\({}^{3}\), energy dissipation decreased for both concretes. The reduction was higher in the lower-strength 90 MPa concrete, particularly at FWR = 60 kg/m\({}^{3}\) (\(-\)55%), compared to the 120 MPa concrete (\(-\)36%). This difference suggests that lower-strength concrete is more susceptible to fiber content, which can degrade load transfer mechanisms and compromise ductility. Further, the transition from FWR = 27.5 kg/m\({}^{3}\) to 30 kg/m\({}^{3}\) reflected an asymmetric drop in the two concrete strengths. While the 120 MPa concrete showed a marginal drop in energy dissipation (\(-\)2.7%), the 90 MPa concrete exhibited a more significant fall (\(-\)6%). This bifurcation indicates the vulnerability of weaker concrete to high fiber content, which will worsen issues like matrix saturation, fiber clumping, and localized stress concentrations. Beyond the critical FWR of 27.5 kg/m\({}^{3}\), the energy dissipation decreased in both concretes. This means that lower-strength concrete is more vulnerable to over-content of fibers since an excess of fibers tends to disrupt the matrix and weaken the load transfer, which ultimately decreases ductility. On the other hand, higher-strength concrete possesses a greater tolerance for the increment of fiber dosage but still experiences decreasing energy dissipation beyond the optimum content, suggesting the need for an optimized strategy of fiber selection. The current research generally points to proper fiber content optimization for achieving optimal energy dissipation in high-strength FRC. Moderate fiber content enhances ductility and energy absorption, whereas a high content of fibers results in performance loss, particularly with lower-strength concrete. The increased resistance of 120 MPa concrete to high fiber content reflects the interaction between compressive strength and fiber reinforcement efficiency. Lastly, the specification of FWR = 27.5 kg/m\({}^{3}\) as the optimum fiber content is of practical value in the design and performance optimization of high-strength FRC for structural applications.