Analysis and Experimental Study of Mechanical Properties of Externally Prestressed Integral Reinforced Frames

External prestressing reinforcement technology has been widely applied at the component level; however, its collaborative working mechanism and seismic enhancement mechanism in overall frame structures remain insufficiently systematized. This paper takes an actual frame structure as the research object and adopts a combined method of ABAQUS numerical simulation and low-cycle reversed loading tests to conduct a comparative study on the mechanical performance of frames before and after reinforcement. Based on the cable shape function and the spatial geometric relationship between the cable and web members, an analytical relationship between cable elongation and web member deformation is established, and a quantitative mapping relationship between the prestress level and the mid-span camber of beams is derived. On this basis, the initial layout criteria for the cable-web member system are determined, providing mechanical input conditions for subsequent analysis. Furthermore, the collaborative stress mechanism of the external cable-web member system, the internal force transfer path within the reinforcement system, and the overall deformation coordination mechanism are further explored. The seismic performance before and after reinforcement is systematically evaluated through core indicators including hysteresis curves, skeleton curves, bearing capacity, stiffness degradation, and reinforcement strain in joint regions. The results show that after integral strengthening with external prestressing, the frame exhibits fuller hysteresis curves, significantly improved bearing capacity, gentler stiffness degradation, and enhanced seismic performance of the structure. Moreover, the numerical simulations and experimental results are in good agreement across the major response characteristics, validating the effectiveness of the analytical model. This study provides a theoretical basis and technical reference for the application of external prestressed integral strengthening technology in seismic strengthening projects of frame structures.