Conceptualization and performance evaluation of a super long span cable-stayed bridge with CFRP cables and CFRP–UHPC composite girders

Facing the challenges in improving load-bearing efficiency and spanning capacity of cable-stayed bridges, this study introduces a novel super long span cable-stayed bridge system featuring carbon fiber reinforced polymer (CFRP) cables, and CFRP–ultra-high-performance concrete (UHPC) composite girders composed of CFRP trusses and UHPC decks. Based on the conceptual design of cable-stayed bridges with a main span of 1800 m, a comparative study was conducted on the proposed system and those using steel cables and steel girders across structural weight, engineering costs, static responses, buckling stability, modal characteristics, and seismic behavior. The results demonstrate the feasibility of the proposed bridge system by leveraging the high stiffness of UHPC decks, the excellent strength-to-weight ratio of CFRP trusses, and the high strength of UHPC grouts in multi-cell CFRP main chords. Compared to the bridge scheme based on steel cables and steel girders, the new system features a 34.6 % lighter superstructure with reduced thermal deformations, enhanced rigidity in lateral bending and torsion, as well as a 30.9 % increase in the safety factor of global stability. Although the initial construction cost is 35.7 % higher, the proposed system offers significant life-cycle economic advantages, with a 21.3 % cost reduction over a 100-year service life. For the proposed structural system, the configuration of the UHPC decks is the primary determinant of superstructure weights; the unit price of the CFRP truss materials significantly influences engineering costs; tensile stress in the UHPC decks and compressive stress in the CFRP main chords are critical factors in terms of mechanical properties. The key construction techniques of the proposed system deserve further research for its real-world implement.