Based on the cable-stayed beam model, this paper studies the nonlinear coupled vibration behavior of basalt fiber-reinforced polymer (BFRP) cables on long-span cable-stayed bridges under parametric excitation. Considering the sag, damping of BFRP cables, and the coupled interactions between stayed cables and the main girder, the nonlinear coupling vibration model of the BFRP cable–beam composite structure has been established. Taking the longest cable of Sutong Bridge as a case study, the nonlinear coupled vibration behavior of BFRP cables under parametric excitation has been numerically analyzed using the finite difference method. The analysis results indicate that (1) under parametric excitation, the large amplitude nonlinear vibration of the BFRP cable will be induced with an evident “beat” phenomenon. (2) Under the same parametric excitation, the nonlinear coupling vibration response and the beta frequency of the BFRP cable were both smaller than that of the traditional steel cable. (3) The nonlinear coupling vibration response of the BFRP cable increased with an increment in excitation amplitude and a decrement in cable force. With the increase in the excitation frequency, weight per unit length, and axial stiffness, the nonlinear vibration response of the BFRP cable increased first and then decreased. Meanwhile, the damping ratio of the BFRP cable had no significant influence on the nonlinear coupling vibration.

In response to the issues of microcrack susceptibility, high brittleness, and unstable mechanical properties of desert sand recycled aggregate concrete (DSRAC), this study experimentally investigated the mechanical performance of DSRAC reinforced with hybrid steel–FERRO fibers. By testing macroscopic properties (compressive, splitting tensile, and flexural strengths) under different desert sand replacement ratios and fiber dosages, combined with microscopic analysis, the fiber-matrix interfacial behavior and toughening mechanism were clarified. The results showed that (1) DSRAC achieved optimal compressive strength when desert sand replaced 30% natural sand, with an obvious early strength enhancement; (2) both steel fibers and FERRO fibers independently improved DSRAC’s mechanical properties, while their hybrid combination (especially F0.15-S0.5 group) exhibited a superior synergistic strengthening effect, significantly outperforming single-fiber groups; (3) the established constitutive model accurately described the stress–strain response of hybrid fiber-reinforced DSRAC; (4) microscopic observations confirmed fibers inhibited crack propagation via bridging and stress dispersion, with hybrid fibers exerting multi-scale synergistic effects. This study provided theoretical–technical support for resource utilization of desert sand and recycled aggregates, and offered practical references for localized infrastructure materials (e.g., rural road subgrades and small-span culverts) in desert-rich regions and high-value reuse of construction waste in prefabricated components, advancing eco-friendly concrete in sustainable construction.

With the continuous growth of the demand for concrete in infrastructure construction, natural aggregate resources have become increasingly scarce. The preparation of concrete using desert sand and recycled aggregates has emerged as an effective approach to achieving the sustainable development of building materials. However, desert sand recycled concrete still confronts critical durability-related challenges when exposed to freeze–thaw conditions. We examined how hybrid fibers (steel fibers and hybrid PP fibers) affect the mechanical performance and freeze–thaw durability of desert sand recycled aggregate concrete, along with the underlying mechanisms. Mechanical properties (compressive, splitting tensile, flexural strength) and freeze–thaw damage indicators (mass loss, dynamic elastic modulus) were tested. The findings indicated that at a 30% desert sand replacement ratio, the concrete achieved optimal initial mechanical properties. For the hybrid fibers group (F0.15-S0.5) with 0.15% hybrid PP fibers and 0.5% steel fibers incorporated, relative to the control group, its compressive strength rose by 31.6%, while mechanical property loss was notably mitigated after 125 freeze–thaw cycles. Freeze–thaw damage models based on the exponential function and the Aas-Jakobsen function were established. Microscopic analysis indicated that the fibers effectively suppressed crack propagation and interfacial transition zone (ITZ) damage. This research offers critical experimental evidence and theoretical frameworks for the application of fiber-reinforced desert sand recycled concrete in cold-climate regions.