###### Abstract  
We established a structural finite element model based on a four-tower partially cable-stayed bridge. We performed a study to determine the appropriate settings of several main parameters of the four-tower partially cable-stayed bridge. Given changes in the stiffness of the main girder, stayed cable and length of cable-free zones in the span, a three-parameter coupling coordination model was constructed. The coupling degree and coordination degree between different parameters are calculated and compared, the primary and secondary parameters affecting the structural performance of some cable-stayed bridges are determined, and a more suitable parameter composition interval is proposed. The sensitivity analysis of the main structural parameters of the four-tower partial cable-stayed bridge has not been published in the literature, and there is no coupling study on the length of the cable-free zone and the stiffness of the main girder and stay cable. The overall structural stiffness was improved by increasing the main girder's stiffness and stayed cable, with the main girder stiffness being the primary parameter. The increase in uncoupled zone length in the span improved the utilization rate of the line within a specific range; however, too long a length led to a reduction in overall structural stiffness. The main girder stiffness was set between \(E_{C}\)\({}^{\prime}\)\(I_{C}\)/\(E_{C}\)\(I_{C}\) = 1-3, while stayed cable stiffness was set between \(E_{C}\)\(A_{C}\)\({}^{\prime}\)/\(E_{C}\)\(A_{C}\) = 0.8-1.4. The length of the cable-free zone in the span was set between \(l_{1}\)/\(l_{0}\) = 0.08-0.15, while the coupling coordination degree was medium to high coordination. The structural performance of the background engineering bridge was improved. However, the conclusion of this paper is more applicable to low-pylon cable-stayed bridges, and it has not been verified whether it applies to traditional cable-stayed bridges. partially cable-stayed bridge; main girder stiffness; cable-stayed stiffness; cable-free zone; coupling coordination +
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[PERSON] et al. [4] conducted a comparative study on the structural parameters of a cable-stayed bridge with main span cross-ties and partial ground anchor system, and used the structural analysis software SAP 2000 to establish a finite element model of the bridge to study the effect of different side main span ratios on the static performance of the bridge. It was found that the side main span ratio had a greater effect on the main girder axial force and anchorage force but insignificant effects on the axial force of the cables. [PERSON] et al. [5], considering economic factors, proposed a partially ground-anchored crossed cable-stayed bridge with reduced horizontal pressure on the main girders, tower height and total cost. A study by [PERSON] et al. [6] reported that the changes in elastic modulus of the diagonal cable significantly affected the cable force, resulting in pronounced deflection and internal force of the main span steel box girder section. [PERSON] et al. [7] conducted a parametric sensitivity analysis on a double tower curved partial cable-stayed bridge and concluded that the main girder self-weight, cable-stayed force, concrete shrinkage creep and system temperature were the main sensitive parameters, and the main girder elastic modulus and prestress tension were non-sensitive parameters. Studies by [PERSON] [8] and [PERSON] [9] investigated the cable-free zone of some cable-stayed bridges. They concluded that the length of the cable-free zone in the mid-span span significantly affects the bending moment and deflection of the main girder. [PERSON] et al. [10] found a good set of cable-free zone for single tower cable-stayed-continuous collaborative system cable-stayed bridges. They proposed a reasonable range of values for the cable-free zone and suggested that the setting of the cable-free zone length should be integrated with various factors. [PERSON] et al.