## 1 Introduction  
With the increasing demand for long-span bridge construction, cable-stayed bridges and suspension bridges have emerged as the primary structural systems for achieving breakthroughs in span length. Compared to suspension bridges, cable-stayed bridges possess greater resistance stiffness, offering superior performance under wind loads while maintaining significant economic competitiveness for spans around 1400 m [1, 2]. In cable-stayed bridge systems, the stay cables serve as critical load-bearing components, transferring deck loads to the pylons and ultimately to the pylon foundations. However, as the main spans of cable-stayed bridges continue to expand, the self-weight of traditional steel wire cables increases exponentially with cable length. This results in pronounced sag effects that drastically reduce the equivalent elastic modulus of the cables, significantly degrading their mechanical performance [3, 4]. Furthermore, the growing cable diameter and cross-sectional area with increasing length and tensile force amplify aerodynamic drag, heightening the risks of wind-induced structural damage. Additionally, the enhanced structural flexibility of super-long-span cable-stayed bridges leads to dense overlaps between cable and structural vibration modes, rendering the system highly sensitive to wind-induced vibrations [5, 6]. This susceptibility may trigger parametric oscillations or internal resonance in the cables, causing fatigue damage at cable anchorage zones and compromising service life [7]. Carbon fiber-reinforced polymer (CFRP) cables demonstrate notable advantages over steel cables, including high strength-to-weight ratio, corrosion resistance, and low thermal conductivity [8]. Its application reduces the dead load proportion of cables, decreases overall aerodynamic loads, and elevates cable natural vibration frequencies. Consequently, replacing steel cables with CFRP stay cables presents substantial potential for achieving span-length breakthroughs in super-long-span cable-stayed bridges. Over the past few decades, CFRP materials have been extensively researched. [PERSON] [9] proposed conceptual designs over three decades ago, yet progress in applying CFRP stay cables to long-span bridge structures remain slow and limited. The world's first CFRP cable-stayed bridge, the Storchen-brucke Bridge [10], features a single pylon and a 63 m main span. Subsequently, CFRP stay cables have seen incremental applications in bridge engineering, including the Herring Footbridge [11]; the Laroin Cable-Stayed Footbridge [12] with a 110 m single span; and Jiangsu University Footbridge [13] in China, the country's first such structure with a 30 m main span. To date, practical implementations of CFRP stay cables have been restricted to pedestrian bridges and short-span road bridges, which operate under low load levels and simplified design conditions. Consequently, these applications offer limited reference value for the construction and implementation of long-span or mega-span cable-stayed bridges. Although existing studies have explored ultra-long-span CFRP cable-stayed bridges, most focus on preliminary analyses of static and dynamic performance [14, 15, 16]. In particular, the research on aerodynamic behavior often neglects the geometric nonlinearity of stay cables, instead simplifying them as single-truss models using the equivalent elastic modulus method [17]. This simplification introduces significant inaccuracies in computational results [18]. To investigate these issues, this study establishes a 1500 m main-span cable-stayed bridge with steel girders and steel stay cables as the baseline configuration. By replacing steel cables with CFRP counterparts while maintaining identical span arrangements, two comparative schemes are developed: a CFRP cable-stayed bridge and a conventional steel cable-stayed bridge. A systematic comparison is conducted to analyze the global buffeting responses and cable vibration characteristics of both schemes.